Iron Revenant

Rank:	Extreme (2 ticks per harm; inflicts 4 harm)
Features:	Empty, patchwork shell of armor and other hunks of metal Wielding iron weapons A low, reverberating voice
Drives:	Fulfill the vow Destroy any who stand in their way
Tactics:	Steadfast attacks Pull in iron with an unyielding, magnetic force

Some vows are held so fiercely that they survive even after death. An iron revenant is an incorporeal force of furious resolve, the unfinished vow of an Ironsworn given horrible form as a construct of metal.
Attacks may slow them down or temporarily break apart their armored form, but they have no flesh to pierce and cannot be killed. An iron revenant won’t stop until their vow is fulfilled.