Saryn is the poster girl for AOE dps and room nuke as well as an incredible self-weapon buffing frame. This build focuses on her borderline infinite map wide raw damage output with her spores which makes her a monster for missions where you're constantly killing enemies, most notably ESO.

Abilities explained:

1: Spores: Spores are your bread and butter, infect enemies and watch the meter in the bottom of the screen that displays their current damage go up proportional to the number of infested enemies. If no enemies are infected the meter will rapidly fall down to nothing so your number one objective is to always have enemies infested. Don't spam this ability as casting it while there's spores actives hurts your meter (Unless, of course there's no infected enemies alive).
Spores spread to other enemies under certain conditions:

• The initial infected enemy (the one you cast 1 on) will always spread.
• An enemy that gets killed by anything other than your 1 will spread (including teammates).
• Spores popped directly by you, your allies or your enemies shooting at them will spread.
• Shooting an infected enemy while under the effect of your 3rd skill will spread.
• Any infected enemy that dies while under your 4 will spread.

2: Molt: Leaves a stationary clone of yourself that acts as a distraction, provides a minor speed boost, and explodes when destroyed or recasted dealing minor damage.
3: Toxic lash: Toxin lash is a weapon buff that scales off of your modded damage and repeats a hit you've already done as tox damage with a forced tox proc.
4: Miasma: Is an AOE nuke that applies 1 stack of viral on to the entire room.
P: Saryn's passive is a 25% duration increase of procs caused by her weapons.

Notes:

• TL;DR for spores: Basically as long as your 1 doesn't kill the enemy itself the spores will spread. 3 helps.

Core:

• Range mods: [Saryn]'s AOE DPS output revolves around having high range for the sake of constantly having enemies infected by her spores. Overextended and Stretch together are borderline mandatory for this. Augur Reach is optional, consider it a flex mod.
• Strength mods: Strength is required for a faster spore growth rate, a higher status chance on the spores, a higher boost in raw damage from her 3 (and [Venom Dose]), mandatory for specific subsumes as well as a neat boost in damage on her 4. Anything between 120%ish and 200% is acceptable but don't go overboard. Due to [Saryn]'s rather tame energy spending habits blind rage is advised but if you decide to bring a stripping subsume for higher level content consider alternative options.
• Enemy radar: Being able to see the position of non-infected enemies is a godsend. And because of the enormous range of your 1 and 4 stacking the aura with (primed) animal instinct on your companion is very much recommended.

Alternatives:

• [Augur Reach]: [Augur Reach] can be replaced with venom dose for more single target DPS. But if you truly want to scale higher you need to swap a few more mods.
• For higher level content swap [Blind Rage] for [Transient Fortitude] and [Streamline] for [Venom Dose] as well as the subsume from roar to terrify. (Another option is keeping streamline and swapping augur reach instead or if you're fine with 100% efficiency going for venom does and augur secrets.)

Non-Alternatives:

• [Revealing Spores]: Although being able to tell, at a glance, which enemies need infecting is nice a keen eye and decent map awareness make this augment a slot waster. Bonus negative points for the fact that you can't use [Venom Dose] on the same build as it. If there were any aura mods worth using over radar I'd theoretically drop the current one for something else and run this exilus but as the exilus slot is more valuable than the aura slot, I can't recommend it. If you don't have PSF or find a slot for it, go for it, otherwise pass.

Economy:

• Duration mods: Duration mods allow your buffs to last longer meaning spending less overall energy on them over a given time period. Primed continuity is enough on its own.
• Energize: Energize is kinda mandatory if you wanna keep efficiency below 100%. It's expensive but incredibly effective.
• Zenurik: Zenurik constantly keeps you topped off and gives you wiggle room between energize procs.
• [Streamline]: [Streamline] alone offsets a chunk of blind rage and hits a sweetspot where the build becomes usable assuming you're using the things above.
• If all else fails, Pads: There's no reason not to always have a few pads to combat unfortunate deaths, leech eximus units, mag procs or the like.

Alternatives:

• Fleeting expertise can be used instead of or alongside of streamline in case the player has no access to energize.
• Transient Fortitude can also be used instead of Blind Rage in case of energy issues.
• On budget builds you can replace [Rolling Guard] for [Vitality] and use [Hunter Adrenaline] or [Rage] to help you manage your economy. But this isn't something you should learn to rely on as it hurts you in the long run. [Regenerative Molt] can also then be used to complete the loop between energy and health but this really isn't something you should do once you have access to spoilermode healing.

Non-Alternatives:

• [Flow]: Although not a horrible choice, due to saryn's lack of burst energy spending (outside of right after being nullified) it's really not needed.
• Narrow minded, yeah, no, don't even think about it range is too valuable on the nuke build.
• [Contagion Cloud]: Although the augment seems good on paper it's extremely gimmicky. There will always be tens or hundreds of enemies that die to your spores compared to those that die by your weapons.

Survivability:

Kill. Nuking the whole map while being on the move is your best bet for surviving. Shield gating stray shots with the use of the the augur mods (on the frame or secondary) helps.
Spoilermode, heal with magus repair or elevate, stun with magus lockdown, run away by spamming slings if needed.
Primed Sure Footed decreases the time you're out of the fight. Be that because of unavoidable walls of fire, hook/bash enemies or your own AOE weapons.
In a pinch you can use your 4 for the short CC or pop a shield pad.

Alternatives:

• On budget builds you can use vitality instead of rolling guard.
• [Primed Sure Footed] can be replaced with a myriad of mods most notable examples are: [Revealing Spores], [Vigilante Pursuit], Handspring, Firewalker or slightly worse options such as Enemy Sense, Mobilize, Power drift, Cunning Drift and so on.

Non-Alternatives:

• Vitality: On higher level content this mod does nothing.
• Regenerative Molt: Molt is your go-to subsume ability and facetanking does not scale well.

Notes:

• Warframe is a game where taking damage is mostly optional and revives are plentiful and are a resource to be used. This means that it's perfectly fine to die from time to time as long as you aren't failing missions.

Quality of Life:

None... Maybe Prime Sure Footed counts here for the sake of self stuns with explosive weapons but that's about it.

Alternatives:

• [Firewalker] or another mobility mod can be used to speed you up, not that you'll need it considering you'll be camping most of the time.
• Arcane Consequence: A QOL arcane meant to increase your mobility allowing you to [Reach] enemies quicker.

Subsumes:

What skill to swap: Molt, it's not necessarily a bad ability, it's spammable for shield gating, offers a decent (albeit underwhelming unless you build for it) speed boost, does some damage when it blows up and works as a diversion, it's just that the other 3 skills are just too synergetic with how saryn works meaning you have no other choice in the AOE build.

• Roar: Roar is the lowest effort, damage boost to your 1 and 4 that actually gets the job done.
• Pillage: Cleanse, armour strip, double shield refresh, spammable and relatively inexpensive. If you need survivability add pillage.
• Terrify: Terrify has become the defacto best strip skill as. Between the fullstrip at just 167% strength, high range that doesn't requires LOS and CC it's truly incredible. The downsides of it include a higher energy cost as well as a lengthy animation meaning you'll probably need to dedicate a mod slot to natural talent or a few shard slots to cast speed.
• Dispensary: In case you can't keep your energy reserves high enough to function, does requires you to slot equilibrium though as well as either having a way to take damage or a pet that carries synth fiber..
• Infested mobility: A better move speed ability than molt, speeding up your parkour and lasts much longer.
• Shooting Galley, with or without the augment provides decent CC.
• Resonator: Just there for the CC.

Non-Alternatives:

• Eclipse: A weapon damage boost only, doesn't really help the AOE damage aspect. Not bad just not terribly useful
• Breach surge: Breach surge doesn't scale with your 3 or [Venom Dose] the fact that you have to spam it on newer enemies will quickly drain your energy. Good on paper but meh in practice.

Archon Shards:

Mandatory shards: None.

Red: Ability Strength, Ability Duration
Yellow: Casting Speed (If using Terrify), Effectiveness on Energy Orbs, Parkour Velocity
Blue: Energy Max

Gameplay:

Cast roar (if you're not using roar you'll need to constantly cast your stripping or utility skill whenever needed) and your third skill. Cast your first ability on an single enemy then kill them with your weapons after this open the large map and look for any uninfected enemy, use AOE weapons on enemies that are near to the uninfected while under your 3 to spread spores. You can check if the enemy is infected through walls by simply looking for damage numbers done by spores. If you're unsure you can make it in time or simply want a damage boost cast your 4 for easier spread and more damage.