Protection from deathbane was a spell used by necromancers.
When cast, this spell allowed a caster to protect an undead creature from spells that were specifically created to harm undead creatures.
In addition to verbal and somatic components, the spell required a material component, ash. During casting, the caster formed a circle of the ash around the target undead creature.
This spell was known to be used by wizards of the Cult of the Dragon.