Hey, lads! AnonymousPepper here. MR18 on PC, and a complete [Mesa] spammer. Pretty sure the only frame I've got more time in is my starter. I'll be your instructor for today on the grand science of Mesa building.

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First, a semi-detailed summary of Mesa's abilities.

Up front, her passive, Marksman's Dexterity. Single pistols reload 20% faster - good for things like Kitguns and Lex Prime, especially since (Primed) Quick Draw isn't a meta inclusion in many builds. Dual pistols fire 10% faster - more dakka with Twin [Grakata], I suppose, but I personally don't find extra fire rate to be that useful most of the time, given that [Lethal Torrent] is used in almost all secondary weapons, plus some use [Anemic Agility] as well, and [Mesa] should always have an Arcane Velocity if possible, so it's kind of pissing into the wind. Lastly, going into battle without a melee weapon will yield you 50 extra bonus (not base) HP. I personally find that even with her good sources of damage reduction this just isn't worth the value of a good melee like Dark Split Sword or [Redeemer Prime].

[Mesa]'s 1 is Ballistic Battery. You turn it on, then as you do damage it charges up. When you hit the button again, your next shot fired will be a fuckoff big gunshot that does a good deal extra damage (though not a significant amount past star chart levels). Ballistic Battery scales with power strength, though it's definitely not a good enough skill to justify putting much strength on her (under ideal circumstances you'll have about 6k extra damage for a single shot). It's not the worst 1 in the game (in fact, it's actually pretty decent as far as first abilities go, but it's massively outdone by her other spells), and it can be very useful for leveling up guns and for when you're leveling your [Mesa Prime] after you've forma'd her. Otherwise, you'll rarely if ever use it. The augment is likewise pointless.

[Mesa]'s 2 is Shooting Gallery. You do a little swoosh and your guns and swords magically do 25% more damage for a fairly long duration. Your teammates also get this bonus, one person at a time for an equal duration each (so if yours lasts 60 seconds, and you're in a four-Tenno cell, each teammate will get the bonus for 20 seconds; if you were in a party of two, the one other would get it for the full duration of 60 seconds, if you were in a party of three it would be 30 seconds per person). This is additive and essentially functions as if your Serration/Point Blank/Hornet Strike/Pressure Point had a +damage value that was 25% higher. This value scales with power strength, but poorly - the final increase is 25% times your power strength, so with this build, which has 155% strength, the total bonus is 38.75%; given that [Hornet Strike] is +220%, one can see why this isn't particularly exciting. Still, it's something. Your teammates will appreciate it if nothing else. Additionally, Shooting Gallery temporarily stuns (for melee enemies) or jams the weapons of (for ranged dudes) three enemies per 1.5 seconds within 16 meters base, about 5.3 meters with this setup, for a short period of time. This is [Mesa]'s only proper crowd control, as well as the only real reason to have range, and while it's good, it's not that good. The augment for this is really not worth it, as it's an extra guaranteed stun at a shorter range that will only be going off once every fifty seconds or so for you.

[Mesa]'s 3, Shatter Shield, is where the real goods start coming in (and they don't stop comin'!). [Mesa] does a little hand motion, and you are now mostly immune to ranged weapons. Shatter Shield is one of the most powerful defensive self-buffs in the game, coming with instantaneous 95% damage reduction and an immunity to ranged knockdown effects such as Ancient grapples and Scorpion hooks (but not AOEs like Shockwave MOAs). You must have at least 119% power strength to cap the damage reduction to its 95% maximum value, which is why it's so important on [Mesa]. Shatter Shield also reflects incoming bullets to enemies within a small radius of you, which is not as good as it sounds, because enemy damage scales far more slowly than their health, shield, and armor values, though reflecting Bombard rockets for free AOE knockdown is cool, I guess. Shatter Shield has a semi-okay augment that gives a chance to stagger enemies when hit by reflected projectiles, but the reflect range is short (11m base, 3.6 in this build) and increasing the range has anti-synergy with her kit thanks to the power strength reduction from [Overextended].

[Mesa]'s 4, Peacemaker, is what brings it all together. A channeled ability (meaning effects like pads, Zenurik dash, Energy Vampire, etc., don't affect her while it's up), [Mesa] stops moving other than turning around, pulls out her exalted weapons (her Regulator Pistols) and engages her autoaim hacks in a circle in front of her out to 50 meters, unaffected by range. She unleashes a hail of perfectly accurate center mass shots (no headshots unless the enemy has their head in the center of their hitbox, like some MOAs, sorry!). The circle shrinks down over time as you fire off shots, but you can just cheaply recast the ability to reset the size.This ability deletes things. You can strip armor from heavily-protected Grineer using corrosive procs, you can pierce Corpus shields with toxin or gas procs, you can melt heavy armor Corpus Index units with constant radiation damage, and of course Infested are a joke. [Regulators] absolutely shit out damage to a degree you would not believe when at full build. This ability scales with power strength, but it's weak scaling - you add 55% in this build to your [Hornet Strike] numbers, 93.75% with Shooting Gallery added on. In any case, you won't need it. Anything at the star chart level dies almost instantly. Anything above that is either Infested and therefore a farce, Corpus and therefore overdependent on shields and getting deleted by toxin damage, or Grineer and getting their armor rapidly melted by corrosive procs. You just click and hold, and things die. The only real exceptions to this are some bosses and other enemies that can't be autoaimed onto - any enemy with a specific weakpoint such as Vay Hek or Sargas Ruk, or an ability-immune target like Nullifiers or Arbitration Drones, have to be killed with something else.

As for the augment. [Mesa's Waltz] is a noob trap. Don't be tempted to slot it. You recast your Peacemakers (4) fairly often anyway to reset the range, so your ideal playstyle is a lot of bullet jumping around and casting 4 in mid-air, which is far better for mobility than Waltz could ever dream of. You can replace Waltz by learning where the best sightlines are for a given tile and just positioning yourself there so as to have to move as little as possible.

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Now, the build. A mod-by-mod explanation:

• Corrosive Projection is the best aura mod in the game, hands-down, and always will be until armor scaling is changed (barring situational picks, mostly on other frames, like [Power Donation] [Nova]). The math works out to something like "free damage, and a ton of it." Take this and never look back. Definitely don't fall for traps like Pistol Amp. Also, formaing your Aura slot to a dash polarity lets you easily swap in Enemy Radar for Index, which is nice.

• [Synth Reflex] pumps your draw speed cheaply and effectively, and draw speed determines how fast your [Regulators] come out. This will often help you clear a room faster than more power strength would, especially at star chart levels where you're one-shotting everything anyway. Remember, do not slot Mesa's Waltz in here.

• Narrow-Minded is perhaps the core [Mesa] mod. You really, really don't need range on [Mesa], but Duration on the other hand is pretty much her core stat. The slightly larger 4 crosshairs are barely noticeable, and the extra CC range on your Shooting Gallery (2) isn't really worth it. Remember, the strongest form of crowd control is death, and Narrow-Minded helps you do it much more effectively. Recasting your 2 and Shatter Shield (3) much less often is enormously helpful, especially at higher levels where you will have to have your 3 up at all times or else you just die. This also improves the energy drain on your 4.

• [Adaptation] is a somewhat controversial pick, but it's just such a huge amount of extra effective hit points, on a frame that has enough tankiness to survive building up [Adaptation] stacks, that I don't think I can really pass it up. You already have 1148HP in this build, accounting for the Umbral set bonus, which is nice, your armor isn't terrible at 85 (that's ~22% more Effective Hit Points, for 1679.6), and most importantly you've got 95% damage reduction from Shatter Shield, which brings you up to 33,592 EHP. Now stack an additional 90% DR from this and you basically only die to Bombards or melee attacks, because that brings you to a whopping 335,920. This also renders you mostly immune to those annoying poison procs, which is another big plus.

• I know I just said that duration is God on [Mesa], but here you're going to take a hit to it in order to kick up another very important stat: your efficiency. Since you will be recasting 4 frequently, either from clearing your line of sight or resetting the crosshair size, you want a high efficiency to make it easy on your energy pool. This also makes it so that you have to have a way lower energy before you find yourself tragically out of mana and with your 3 down while facing down a room full of level 100 corrupted lancers - a thing that happens to the best of us.

• Umbral Vit... this is a giant chunk of HP. This is what makes your multiple sources of damage reduction work. You need this. If you don't have Umbrals, run regular [Vitality] instead. There is no excuse to not have an HP mod. But if you possibly can manage it, the Umbrals are significantly better.

• [Flow] is just a good mod. It lets you function during energy reduction sorties and gives you way more comfort space to cast your spells in. Just take it. You could fit Primed Flow in here if you swapped Lightning Dash out for Mobilize, or used an Umbral Forma, but... more on that later.

• Remember what I said about Duration? Yeah. Primed Continuity gives you more of it. Case closed.

• [Umbral Intensify] is nice not so much because of the extra power strength but because it's a power strength mod that also buffs your [Umbral Vitality]. You only need 119% strength to cap Shatter Shield, and more doesn't do that much for you, true, but why not? You're already going to be using a slot on strength anyway, so why not make it one that makes your health mod better too?

• Finally we have [Lightning Dash]. You spend more time in Warframe bullet jumping than any other activity, period. Why not make it better? Lightning Dash and its elemental counterparts are the best mods in the game numbers-wise, and they also have the advantage of looking freaking great - plus, remember, electric procs stun, so if you need a stun that badly, there's that too. But mainly remember, fashion frame is the true endgame. If you want to have [Primed Flow] on instead, though, you can swap [Lightning Dash] out for Mobilize and use one less forma in the process. The choice is yours. You lose 4% off the +bullet jumping stat (or 1/6 of the total increase), and of course the excellent fashion, but you'll get more energy out of the deal.

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[Mesa] can be played in any game mode, though she struggles some in rescues (for lack of things to do) and spy missions (no stealth or ability to bypass barriers, and she doesn't one-shot things generally so, for example, shooting a Grineer Sensor Regulator will just trip an alarm). She's also subpar in Arbitrations, because she has no way to kill the drones through abilities - at which point, why not just bring an [Oberon] or something and kill them with a Plasmor while also keeping your teammates alive with Phoenix Renewal? Lastly, Mesa sucks ass, relatively speaking, at fighting many bosses, since they're immune to her hax-tier Regulator damage. One day DE will let you lock onto Lephantis' mouths, but it is not this day. Oh well, at least you're better at it than [Vauban]. The same logic applies to Eidolons, by the way. Your damage buff is nothing compared to what a, for example, [Rhino] or [Chroma] could accomplish, your Shatter Shield doesn't apply to a lot of the damage output from their AOE abilities, and your [Regulators] can't lock onto Eidolon parts or kill Vomvalysts. I am not currently max rank with Vox Solaris, but I understand the same conclusion applies to Orb fights - don't.

Also avoid bringing her to Elite [Sanctuary] Onslaught unless you've gotten good at positioning, as Simaris will get upset at you for recasting 4 too much if you're not careful.

On the other hand, [Mesa] dominates Exterminate and Defense missions. She can clear the map like nothing else, short of a [Saryn], [Volt], or Maimquinox, and is highly mobile with the addition of [Synth Reflex] and a bullet jumping mod. [Mesa] is also generally quite good at open world missions, despite the limited range on her [Regulators], since a lot of them revolve around just killing things or defending objectives.

Best of all, [Mesa] is one of the two best damage frames for Index, the other being [Duality] [Equinox]. Get some radar mods into your build and go make the brokers' lives difficult. Stick it to Nef Anyo and rake in the credits in the process. Just make sure you leave picking up the credits to your [Rhino] buddy, and watch out for the AOE attacks of some of the brokers.

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Arcanes and such!

• Bring an Arcane Velocity. This is not a suggestion, this is a command. Velocity makes your Regulators go from terrifying to war crimes.
• Your other Arcane is up to you. Arcane Energize is of course the best option most of the time, since you're an ability-dependent frame, but it's both expensive and not entirely necessary if you're willing to make use of pads or have a [Trinity] buddy. I actually quite like Arcane Consequence; it's cheap and makes you even better at bullet jumping. Other options include Arcane Momentum, for those Rubico Prime spammers out there - in fact I highly recommend it for open-world missions, given just how good Rubico P is at deleting dropships - and the various tank arcanes such as Arcane Grace.
• Magus Repair is probably the best option for self-healing out there, when taken in combination with its ability to heal the whole squad in the process. If you don't have it, a good melee weapon with [Life Strike] on it would do just as well (this is one of the reasons I never take advantage of the HP boost part of Mesa's passive).
• Your spells do synergize pretty well with the Kitgun arcanes. Pax Bolt bumps up the strength of your 2 and 4 a little, and puts you to maximum efficiency for casting your buffs, and Pax [Seeker] gets buffed up by your 2, which can be the cherry on top of some already quite broken weapons. Don't ask me about Zaw Exodia arcanes, I've steered clear of those bad boys out of disgust for the power creep. (Says the guy making a [Mesa] guide and recommending Kitguns!)

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Regulator builds are fairly simple. [Hornet Strike], [Primed Pistol Gambit], [Primed Target Cracker], [Anemic Agility], [Lethal Torrent], [Barrel Diffusion], and your choice of two elementals. For Grineer and Corrupted, run dual stat toxin and dual stat electricity for maximum armor stripping. For general Corpus, run either dual stat toxin and 90% toxin (most effective) or dual stat heat and 90% toxin (memey and fun, but not as good). For Infested, let's be real you could run Magnetic and still do just fine, but I'd recommend 90% toxin and 90% electricity to kill Ancients faster.

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Lastly, weapon recommendations! You can really bring whatever you want, since Mesa is so goddamn good, but if you're looking to be an OpTiMaL sWeAtY tRyHaRd, listen up.

• Your primary should make up for a weakness that Mesa has. For one thing, Mesa's long-distance capability is limited thanks to the 50m range cap on [Regulators]. [Rubico Prime] is your best bet, though [Vectis Prime] is also a good choice. Alternatively, [Mesa] lacks AOE armor strip, so if you want to strip from multiple guys at once, you could bring a weapon like [Ignis Wraith]. [Ignis Wraith] also is very good at killing Arbitration drones, if you want to be a masochist and bring [Mesa] to one anyway, or for AOE gassing the crap out of the Corpus; Plasmor fulfills the same function. Tigris Prime is also an option if you want single-target burst, but Regulators are usually better for this. Definitely don't bother with normal rifles.

• Your secondary should probably be a kitgun, or another high-end single weapon, to make best use of your passive. I like single Lex Prime personally, but I'm old-school. Alternatively, you could try something like Staticor for AOE armor shredding/status proc memes, but I don't think that's as good.

• You should have a melee weapon unless you've got a good Magus arcane or other means of self-healing handy. The primary purpose of melee on [Mesa] is to give a reliable way to heal up and to force Infested to back the hell up, or to apply a ton of armor strip in the case of [Redeemer Prime]. I would suggest something that comes out fast like Dark Split Sword with [Life Strike] on it.