Nodal Regeneration

Your body processes magic so effectively that you can induce true regeneration, replacing limbs and restoring organs. You can cast Regenerate once per day as an innate spell. Instead of being deactivated by acid or fire, your regeneration from the spell is deactivated by cold, which slows your metabolism. You can target only yourself with the spell, but you can Cast the Spell as a reaction if you're reduced to 0 Hit Points by a non-cold effect.