Undertow is a great ability to do scaling damage against high level enemies. We utilize a subsumed armor stripping ability because Undertow struggles against armor, especially as enemies scale well into the four digits.

Fire Blast is chosen because we can combine it with [Corroding Barrage] to significantly cripple enemy armor with little stat investment. Shuriken should be used with [Seeking Shuriken] (over [Corroding Barrage]) when heading to level cap and Pull can be used if you're going against Infested to more easily wrangle enemies.

Strength is kept at 100% because of the way Undertow's damage scales. Even at 400% you only double the speed at killing enemies at the cost of ruining all of your other stats. If you run [Seeking Shuriken] replace one of the range mods with [Umbral Intensify] so you can get a full armor strip.

Efficiency is maxed so you can stay in Undertow as long as possible. It also helps you to spam your other abilities.

[Corrosive Projection] is needed because [Corroding Barrage] no longer completely strips armor after the corrosive nerf. Undertow has trouble killing through armor. Replace it if you're running [Seeking Shuriken] or going against unarmored enemies.

[Enemy Radar] mods help us to find enemies. Due to the nature of the build we need to sometimes seek out stragglers.

[Rolling Guard] protects you in between Undertow casts. You'll eventually run out of energy so the invincibility gives you time to grab energy orbs to proc Energize.

[Corroding Barrage] can be replaced with any other augment if you're going against unarmored enemies or you have another way to strip armor.

Arcane Aegis gives you additional time to roam outside of Undertow if it procs during [Rolling Guard]. If you don't like the RNG aspect of it you can replace it with any other arcane to suit your playstyle.