The Immovable

Iron Skin's value is base armour times a stack of multipliers, and Strength enters that product three times: Parasitic Armor scales on Strength (about 6185 armour at 398%), Ironclad Charge scales on Strength (about 199% total- armour increase per enemy hit), and Iron Skin itself takes Strength as a final multiplier.

Primed Redirection feeds Parasitic Armor through shield capacity, and Arcane Expertise converts Strength into more shield on top.

Arcane Battery gives up to 1000 energy max at high armour, which frees the Primed Flow slot.

1.

At mission start, cast Parasitic Armor then Iron Skin for about 30k as a buffer, which also maxes Arcane Battery.

2.

Refill energy (Zenurik, Grimoire Xata Invocation, Tenet Glaxion).

3.

Optional extra armour: health orbs for Health Conversion, melee kills for Melee Fortification, and so on.

4.

Group a crowd (Magus Anomaly, Exodia Hunt, Vazarin snare).

5.

Cast Charge through the group for the Ironclad Charge bonus (12s).

6.

Cast Iron Skin twice: once to dispel, once to recast while Ironclad Charge is still up, locking the inflated armour into the Iron Skin value.

7.

Keep Roar up.

Duration keeps Roar near 40s and gives comfortable Ironclad Charge and Parasitic Armor timers for setup.

Efficiency is floored; the combo costs about 200 energy, so you need a start-of-mission energy source.

Range is untouched at 100% for a decent Charge line and Roar radius.

Strength is the entire build.

Transient Fortitude, Blind Rage, Umbral Intensify are the Strength stack, with Primed Continuity holding Duration.

Ironclad Charge is the mandatory armour multiplier.

Health Conversion is a stacking armour source.

Primed Redirection deepens the shield pool for Parasitic Armor.

Iron Shrapnel is optional recast control.

Growing Power aura for another 25% Strength on proc.

Iron Shrapnel becomes Augur Message (Roar uptime), Augur Secrets (Strength) or Equilibrium (energy).

Umbral Fiber and armor mods are deliberately excluded: base armour is only 290, so they add almost nothing next to the Strength sources.

Parasitic Armor is the build.

Alternatives if you cannot get it: Elemental Ward (Cold) for about 1291 armour, then Defy, then Warcry.

Empower works but needs a recast before every ability.

Madurai for a 40% Strength Sling perk, which is the best choice for maximising Iron Skin.

Vazarin for a grouping ability.

Zenurik for energy plus 20% Strength on next cast.

None from the frame beyond Roar.

A slam melee with Melee Fortification adds more armour to the stack.

Otherwise bring whatever kills.

Iron Skin, and only Iron Skin.

It has no innate regen, so when the pool is gone you redo the combo.

Toxin bypasses it entirely, so bring a way to cleanse or avoid toxin.

Arcane Battery plus a start-of-mission source.

Once Iron Skin is in the millions you only cast Roar every 30s.

Toxin.

Endurance past the point where a single hit exceeds even a multi-million pool.

The setup combo is a ritual you repeat every few minutes, and a botched order gives a fraction of the value.

A non-helminth Iron Skin tank.

A Roar buff build sharing polarities.

An endurance Nourish non-tank variant.

A Mecha Pulse armour-meme variant.

Strong: effectively unkillable in most content once set up, strong team Roar, conceptually simple.

Weak: does zero damage itself, toxin-vulnerable, setup ritual, no regen so the pool is a countdown.

Players who want to not think about survival at all and just carry a weapon, plus a Roar for the squad.