Detonate Dead

Detonate Dead is a spell. However, it deals damage that isn't spell damage.
We've learned that players want the "Spell" tag on gems to not be associated with spells that deal non-spell damage, so they get the "Cast" tag instead, to show they're still spells you cast, but spell damage modifiers won't affect them.

"

YohSL wrote:

There is one thing that particularly bugs me about this skill, which is why doesn't it work with the Necromancers Spirit Eater or Ascendants Necromancer passives?

It does.