Touch of Death

Epic Boon Feat (Prerequisite: Level 5, have to reach 0 hp from the attack of a greater undead or above and live)

Having been struck down by a powerful undead creature, a touch of magic has permanently scarred your soul, leaving your physical body "altered"

You gain the following benefits.

Near Death Experience. When you are at less than 12HP, all undead creatures roll disadvantage when attacking you.

or:

What Doesn't Kill You. When facing 3 or more undead creatures, roll an extra 1d8 points of damage to an undead creature you hit.

Must have:

Soul Scar. You become resistant to necrotic damage, but vulnerable to radiant damage.