Undying Sigil

Undying Sigil is a Necrobinder-only Shop relic that reduces incoming attack damage by 50% from enemies whose Doom accumulation equals or exceeds their HP. If you're building Doom, it's a major defensive bolster — but in non-Doom builds, it's completely meaningless.

Being a Shop relic, you spend gold, and buying it without a Doom build makes no sense. The effect also doesn't apply to enemies who haven't accumulated Doom, so in multi-enemy combats only some foes benefit. As defensive reinforcement for a Doom build it's decent, but priority versus other Shop relics requires careful comparison.