This guide explains some hopefully simplified details of frontier defense that the game doesn't clarify or doesn't tell at all, as well as explaining the roles of items and titans according to what I personally experienced over about 300 hours of playing the mode from easy to insane. It's important to note that this is not gospel and I myself am still not sure of certain things. Some things I initially imagined to be bad when playing, like nuke rodeo, turned out to be absurdly good after I took the time to actually try them out in better detail. The dynamic of the game shifts according to the difficulty, and suddenly certain titans are easier than others, or maybe just more desirable to have.

I myself am a person that gets confused when people start pulling "numbers this, numbers that", "specifically do this specific thing at this specific time or else we all ♥♥♥♥♥♥♥ die, and also do it only in specific maps" and the list goes on. I tried to avoid needless numerical values, needless comparisons and for now just wrote this guide off the top of my head. I might've forgotten something I wanted to add, but I also might've not. I tried to digest the information based on anecdotal evidence, so I could then give digested information to other people and hopefully give them a better view on what to do and not do in frontier defense and its inner machinations. It assumes basic knowledge of the aegis upgrades and a maxed aegis titan, as well as the basic information of the titan itself - basically everything you can already read on the menus.

• Talk to people - it's a cooperative mode, even if you have some inherent competition. Call out mortars when they go unpunished too long, form strategies if something isn't working well and suggest things when fit - if your team is in good condition, your victory is in good condition.

• If you're not going to use your money, put it in the bank - you may already have enough arc traps, shield boosts and sentries, but your teammate might need a battery and is just too much of a shy ♥♥♥♥♥♥♥♥♥♥♥♥ to open their mouth.

• Let everyone get a battery on the wave 1 titan, if it shows up - a shield means less damage taken and less need to spend money on batteries.

• Let your Monarch execute titans on earlier waves - the faster they build their core, the more smokes (and upgrades, obviously) they have and the sooner they can support your team. Also use your ♥♥♥♥♥♥♥ smokes as Monarch.

• Don't bodyblock your teammates - oftentimes I'll have people who blatantly jump in front of my shooting in ways that completely lack any form of situational awareness.

• Keep in mind who you can bodyblock - Legion can fire through anything, allies and enemies included; Northstar needs the piercing shot kit for that, but using it will have the same effect. This means both of them can line up with teammates and shamelessly use them as shields - whether it's consensual or not is up to the laws of the land. Scorch can also do it with firewall and flame core, but traps and the launcher still get blocked by teammates.

• Honestly, let anyone execute titans if they want - some people will definitely just have a monkey brain and start mashing melee the soon they see a striped bar, but other players do so because it's a convenient moment (lone titans or single-digit enemies remaining) and they want to build their core. It's also worth dooming titans near teammates who are in danger to abuse their monkey brain and give them a safe kill.

• Avoid sweating for executions - you don't need to, as a Ronin, dash from the literal opposite end of the map just to get that extra 5% core in the middle of a crowd the Scorch is already killing and needs no help on.

• On lower difficulties, you most definitely can play only as a pilot - using your titan as distraction while spamming anti-titan weapons, ordnance and nuke rodeos is not only fun, but also works well enough that you can rise to the top of the scoreboard doing only that. People love pointing out combat score as a general performance, so flex on them when you beat their piloted Scorch with a Thunderbolt and pocket smoke.

• I actually encourage you to try a couple rounds or matches strictly as a pilot - the higher difficulties need a more precise piloting than just sitting on a roof and spamming until you get your titan back. Be proactive, be vicious and learn the patterns you need to survive when your titan is gone without the need to hide and clench your ♥♥♥♥♥♥♥ - the more you learn, the better you are. When I say strictly, I mean still drop your ♥♥♥♥♥♥♥ titan.

Amped weapons: It's used to increase the damage of your primary, pistol and anti-titan weapons; the increased damage means you'll get your titan back sooner in the occasion you're forced out of it. Goes away on pilot death, so don't get cocky when doomed; otherwise you could make it needlessly harder to get your titan back if you're doing nuke plays and other tomfoolery.

Amped battery: It's used to heal your titan roughly two bars, give it shields and add core charge. It also can be used to speed up your titan meter, in case you find yourself without one at the end of the round and have nothing to shoot to build it back up. Each battery use on an ally gives 24% titan meter to you. You can also hold onto it if you're doing the whole nuke pilot thing, so you can give someone a small health boost in case ♥♥♥♥ hits the fan.

Nuke rodeo: Possibly the least used item (I personally almost never see anyone use it) in frontier defense. It triggers a nuke on the titan you rodeo when you hold the rodeo key after mounting; the consequent explosion will affect other nearby enemies, similar to a nuke ejection, except without needing to expose your titan. If your team is struggling with a crowd, it can be used for fast clearing without needing Scorch, piercing Northstar or Legion to do the hard work and take damage while doing so.

Arc trap: A permanent shock trap. It can stun Legions out of their gun shield (meaning nukes as well), instantly kill ticks, halt anything else that isn't an arc titan and, most importantly, damage titan shields (the bar) - stalkers, however, get provoked by the shock's damage and start sprinting. Other arc traps can halt the sprint with a stun, but not cancel it back to their standby state. Place it in a way that gives max coverage to an area (usually), while also considering height in case there are drones involved, since those also get stunned by the traps and it can prevent the destruction of sentry turrets when done right. Works on line of sight, in case you want to synergize the stun with turret placement for a lot of shooting and little vulnerability by placing it around a corner.

Sentry turret, pilot sentry, whatever: The almighty minion killer. It gives your team (some) breathing room by allowing them to focus on the many titans and reapers that can come with each wave. Enough turrets will down reapers and maybe titans, but I recommend not focusing them on that (you lazy ♥♥♥♥). Their best use is preventing attention from being diverted to a group of four (4) grunts preventing the harvester shield from regenerating, which is something you really (really) don't want on higher difficulties. Due to their delay to lock on, placing them around corners and near enemies is a bad idea, since it just gets them destroyed and someone has to repair them; instead, position them far from enemies and where they can see what they're going to shoot before that what sees the turret. Usually means close to the harvester and overseeing a large area from a distance, but can also be used with a height advantage on the blind spot of an enemy, like the second floor of the building at the end of the middle path in Exoplanet. The idea is to either kill the target before it kills them, or just give them another target to focus on before they actually see the turret.

Havester shield boost: The patrician taste. It immunizes your harvester shields for 5 seconds while completely refilling its shields, which means it's very useful to counter nukes and give that little extra gas to the harvester when you can't immediately deal with a small, yet sustained drain on it, such as mortar units and minions that destroyed a turret. Some people try to maximize the boost by timing it just before the shields go down, which usually means they're a legend and see the future, or they'll get cucked by a small unpredictable burst damage that catches their timing off-guard and ruins the flawless defense bonus they were trying to go for. As with amped weapons, don't get cocky and know your limits - if you have to use it while it still has 25% shield left, you have to ♥♥♥♥♥♥♥ use it and there's no inner mental discussion on minmaxing (you lazy ♥♥♥♥).

Shield grunts: Exclusive to master and above, they use a shield that keeps itself in front of them most of the time, which causes an arc grenade's effect on you if you go through; I don't need to tell you why that's bad in the middle of a group of enemies. Flank them or nade them and you'll be fine; you can also punch through their shield if it's safe enough around them.

Stalkers: Spectres with an exploding crit spot on the back that causes them to do several small AoE pops and then end with a big AoE pop that can even hit players wallrunning the top of the harvester; at the first spark of damage, they switch from walking to sprinting, so either shoot the legs first and pop a grenade, or build confidence in your headshots and go all out. If they're exploding at the harvester, there's nothing more you can do; focus on something else instead. Punching them with a titan outright destroys them without explosions, however, so don't waste ammo if you don't need to. You can also ignore their stomp explosion by just not moving while they walk under your titan. They carry an EPG on hard and above.

Mortar spectres: Spectres that set themselves at predetermined spots of the map to fire mortars at the harvester; sometimes the icon still shows up without any enemy at the actual icon, but this means one of them got lost somewhere in the map and isn't an immediate threat, unlike active mortar units. They use a cover shield after setting up on hard an above.

Ticks: They're not exactly exclusive to frontier defense, but you see a lot more of them due to them becoming a normal enemy, instead of a player boost. They will explode when triggered by arc traps, but are surprisingly resistant to small arms fire; they also have a massive blast radius and many people accidentally kill teammates by shooting one, so for the love of everything sacred: situational awareness. Treat them like the thing that will completely ruin your day, because that's exactly what they do.

Plasma drones: Flying small-ish enemies that deal a lot of damage to the harvester. Their biggest enemy is the turret and their second biggest enemy is Ion's splitter rifle.

Cloak drones: Dodgy enemies that seem to have something weird going on with anti-titan weapons. They can cloak several units and hide them from your map under the cloak drone icon, which can and will involve a crowd of enemies, so watch out. Tone also can't tag cloaked enemies, so do the Tone pilot a favor and don't force them to use a slow single-shot weapon against a tiny target that isn't high enough to take reliable splash damage.

Arc titans: Ronin titan that has an arc field which can destroy the harvester's shields in a handful of seconds; dooming them cancels the arc field. The game says they're immune to arc effects, but I've seen them getting stunned by arc traps before, so ♥♥♥♥ if I know what actually happens - do kill them fast, though.

Mortar titans: Tone titan with the brute rocket launcher (I miss you, brute); high ♥♥♥♥♥♥♥ priority target that will deal sustained damage to the harvester as soon as they set up the mortar. While one alone might not do much, every tiny damage blocks shield regeneration, so send someone to delete that thing as soon as it shows up. When you got four? Man, you're ♥♥♥♥♥♥.

Nuke titans: Slow-moving Legion (redundancy?) that blows up its own core (hence the name) instead of entering doomed state; their shields will be a pain in the ass for most titans to deal with, but since they're the enemy that can deal the most damage to the harvester (aside from the ♥♥♥♥♥♥♥ Scorch auto-titan) and often come in waves, they're basically the thing you should be headbutting with to not reach the harvester at any costs. They get stalled by pilot and titan smokes, so put that key to work and don't save your cores for that one time that will probably come too late; the more smokes you have, the less they'll move.

Disclaimer: When I mention "priority", I don't mean "drop everything you're doing to go to the other end of the map to kill a lone reaper before the Scorch tries it", but simply "if you have the option and it's not going to cripple your situation, go for it.

Ion: The "I do everything, but am good at nothing, except doing everything" titan. You're good at killing individual titans, sure, but when a line of them comes you're going to be completely ♥♥♥♥♥♥ until you can get your core. Ion is great at killing lone titans and reapers (the latter is actually what the reflex cannon upgrade is for); this means you're one of the poor sods to go after mortars, since you can down them fast as ♥♥♥♥. Her entangled energy kit allows you to regen energy while getting crits with the splitter mode, rewarding your aim with infinite energy; this means you'll be able to keep a laser shot and splitter combo endlessly if you're accurate enough while also dumping tripwires for minimal extra damage, or maybe just spamming vortex shield and critting the energy spent back. Grand cannon is the other upgrade that can be used effectively, allowing Ion to better take down titans with laser core on higher difficulties, but sacrificing the sustainability of entangled energy. The rest of the kits are honestly ass in comparison.

• Priority, including for your core: Minions, drones, reapers and lone titans, specially mortars.
  
• Not priority: Conga conga conga lines (unless core).
  Keep in mind you can combo reflex cannon on minions, drones and reapers to keep lasering titans for longer, but that's some big brain and surprisingly tough ♥♥♥♥ to do on such a tight timer. To maximize core efficiency, you can graze titan lines by firing the beam slightly to the side or above them, because the hitbox for the damage is actually wider than the hitbox that stops the laser from going through objects.

Scorch: The area denial specialist that shines because the AI doesn't understand fire. You're the god of killing lines and stacking damage on slow titans; you also are one of the two titans to bring the middle finger to arcs with thermal shield and the healthiest base chassis. Play in spaces where the titans can't dodge your fire and always make an effort to line them up with firewall. Keep in mind that any fire can trigger your incendiary traps, so you can lay down firewall and just throw in some traps without needing to detonate them with your thermite launcher. The wildfire kit is great for harassing titans at ranges Scorch has trouble setting fire, while the tempered plating kit allows Scorch to stack thermal shield on top of firewall and explosive traps, fuel for the fire is great for lines of weaker enemies and scorched earth benefits the spammy nature of his core. I can't say I particularly care for inferno shield, but it might have specific uses. If you use your core from far enough, you can get back some charge due to the way the game handles the meter.

• Priority: Conga conga conga lines and tight spaces.
  
• Not priority: Titans in the open and reapers (very dodgy, but your core can take care of them).
  Your thermal shield also destroys drones easily, so don't waste time trying to hit them with the launcher.

Norfstah: The projectile sniper titan for all people with massive phallic objects. Her performance varies according to her kits: piercing shot is the second line killer of the mode and the one I recommend the most, due to how much her overall damage increases and how the default railgun cannot pierce anything; enhanced payload can be nice, but the performance pales in comparison to piercing shot enhanced payload actually reduces your cluster's DPS, as per some complex math that was posted on Leddit; finally, twin traps turns Northstar into a CC master and can be used to halt lines from reaching the harvester, which is a fairly safe way to play in comparison to trying to outdamage everything's movement with piercing shot - do keep in mind twin traps will often use both traps on the same titan if you just lob it foward, so tickle your basketball memories and get creative with bouncing them on geometry. She is the second middle finger to arcs due to her traps, so make sure to use them a lot. You can place a maximum of four (4) charges before the oldest trap disappears, so that's four traps without twin traps and eight with.

• Priority: Sniper titans, anything in a line (piercing) and/or dangerous titans (not piercing).
  
• Not priority: Minions and drones (lob cluster and keep moving).
  Seriously, spam those ♥♥♥♥♥♥♥ traps.

Ronin: The local weaboo that everyone uses with the highlander kit. Honestly, I can't dispute the effectiveness of it and it turns Ronin into a dash-spamming titan killer for as long as the user can sustain that stupid thing. If you have some self-respect, however, you can do it the fun way: thunderstorm, temporal anomaly or phase reflex. Thunderstorm allows you to spam arc wave, while temporal anomaly fits your hit-and-run tactics by allowing you to escape more often. Phase reflex is for immunity when doomed, giving you plenty of leeway to nuke the ♥♥♥♥ out of everything. I would say it's the titan that requires the most mechanical skill aside from Ion, due to Ronin being squishy, reloading often and being a short range titan (the AI's accuracy and damage is merciless on higher difficulties). His melee damage upgrade allows reapers to be staggered on a melee attack, so you already can tell what this means for him. Alternate between dumping shots and taking cover, while also going for executions when you have time and need core. Yes, just because I don't use highlander, it doesn't mean I don't use sword core at all.

• Priority: Minions, cloak drones, reapers and lone titans.
  
• Not priority: Conga conga conga lines.
  In case you don't know, all melee attacks are great for taking down minions in a single hit. Ronin just shines there because it's already within his range, unlike every other titan.

Tone: The melodic explosion specialist of the gang and most hated titan of multiplayer, aside from that 360° sword block weaboo ninja. Tone easily snipes minion crowds (that means mortar spectres) and can setup locks onto crowds of larger things for a big and beautiful payoff. Her particle wall is the Scorch-cucker and her sonar increases damage taken, so be sure to spam that on crowds. Among her kits, enhanced tracker and burst loader are the worst, with rocket barrage being probably best for single target DPS and reaper breakpoints, while the wall kit is pretty useful with its enhanced duration and the sonar kit is godlike in dealing with crowds and setting up double rocket combos (shoot, shoot, sonar, rocket, shoot shoot, rocket). Her ordnance shares the beauty of Monarch's, which is a big "♥♥♥♥ you" to other particle walls. When a Tone uses it against you, shoot around the shield at a wall or the ground, using the splash to get a lock; after you get the lock, fire tracking rockets at the shield to easily dispatch it. This also means that rocket barrage is the shield killer, but as long as you damage it enough for your teammates to easily destroy it before it's over (and consequently save time), the other kits should be fine.

• Priority: Minions and literally anything you can lock on to.
  
• Not priority: Being stupid, tbh.
  Playing Tone, adapt yourself to the fight to compensate for the weaknesses of other allies. If there is no long range titan, that means it's you. If the Northstar is fighting the sniper, that means you shoot the rest of the ♥♥♥♥. If no one is going after mortars, just guess who does it.

For we are many: The actual hardest titan to play, I'd say - a lot of reloading, getting punished by nuke shields and needing to line up titans while Scorch has none of that and allows turbo engine without issue; you don't have to worry about titan kits with Legion, since he has all of them. Your job is basically Scorch's, except the moment a nuke puts up their shield, you enter a frustrating stalemate. Manage your power shots well, predict distances and intelligently use your firing mode switch, as well as your positioning because just being good at shooting things will not save you from being massacred on higher difficulties. Your main objective is getting smart core, since that's 12 (twelve!) more than 12 (twelve!) seconds of pure infinite ammo and aimbot - to do that, you use lines to stack long range power shot and gain core as fast as possible, or just point blank them with the close range variant to also push them back. If you see nukes at low health, don't hesitate to CR power shot them and skip the explosion, since you keep your range intact and prevent the big "♥♥♥♥ off" zone on anyone nearby. As much ♥♥♥♥ as I give Legion, it's immensely fun to set up doomed bypassing on a crowd and just mindlessly smart core everything in sight.

• Priority: Conga.
  
• Not priority: Minions, drones and anything not lined up (CR power shot them instead of wasting ammo whenever you are able to).
  You can aim smart core around while keeping the target in the lock zone to hopefully angle your shots a bit to crit what you can't crit aiming straight, like ogres and Ronins; it's weird and doesn't really work flawlessly, but it is what it is.

Monarch: The punching bag of frontier defense. You start sucking ass and need to hoard executions on titans, as well as reaper killing blows and minion chains, to build your upgrades as fast as possible; not because you absolutely need it, but it's still a pain in the ass to spend multiple waves farming it. They also made it so that healing doesn't build core, so ♥♥♥♥ you for trying to play healer I guess. Since Monarch is divided into upgrades, this gets a bit tricky.

• Tier 1: Arc rounds increases your magazine size on a horde mode (hint-hint) while also deleting titan shield bars and sucking thermal/vortex dry - this saves time and saving time is great. Missile racks is great for taking down shield abilities (the default ability already does it, but MR enhances it) and easily dispatches minions - keep in mind it takes longer to fire. Energy transfer varies between "but I hit him, why didn't the shield go up" and "thanks m8".
  
• Tier 2: Rearm and reload increases your DPS by virtue of reducing the time you spend not shooting, while also rearming faster - less downtime, more pew pew. Maelstrom is a snowball upgrade that keeps feeding itself when used on crowds, but can backfire if you don't catch enough titans, or if they deal too much damage to you. Energy field means you can shoot at the ground and affect anything in the area with both siphon and transfer. This means AoE healing and more shield stealing.
  
• Tier 3: We don't speak of MTM; ♥♥♥♥♥ ass crappy ♥♥♥♥ upgrade. Superior chassis is good, but your survivability comes more from regenerating shields and the health is just a safety net. As far as I know, batteries also don't heal percentages, so you won't get more health from batteries with superior chassis. Since shields negate crits, the crit negation portion is also kinda moot if you manage your shields well. Accelerator increases your DPS, and that saves time - what do we say to saving time?

Monarch's kits are very biased. Shield amplifier barely gives you a bonus, but I theorize it can stack with energy field, giving you 50% more (of the base value) hitting two metal enemies, 75% for three and so on - take that with a grain of salt, since I never tested it. Energy thief will give you a battery on an execution and passively increase core generation, meaning executions give more core, HEALTH, and you get more core outside of them as well. Rapid rearm makes it so that you can combo two siphons earlier, which is useful, but nothing near energy thief. Survival of the fittest doesn't work well in frontier defense, since it'd benefit from the executions you now don't have.

• Priority: Minions, drones (please shoot the ♥♥♥♥♥♥♥ drones) reapers and lone titans.
  
• Not priority: Titan crowds, lines.
  Boy, Monarch was big.

Just so I don't forget to make the section, in case people have their own, uh... questions.