Below is a snip. I think the Golem and myself are reacting appropriately but the zombies don't seem to be. I'm not sure if that's intentional or not.

The questions is: Should the damage not be reduced or negated?

A flesh golem is seared by the black flames of the Archmage of Eternal Night's spell.
A flesh golem is unaffected by the Archmage of Eternal Night's blackfire nova!
A zombie of the old dwarf is seared by the black flames of the Archmage of Eternal
Night's spell.
The Archmage of Eternal Night's blackfire nova does UNSPEAKABLE things to a zombie of
the old dwarf!
A zombie of a gorgeous silver-haired elf is seared by the black flames of the
Archmage of Eternal Night's spell.
The Archmage of Eternal Night's blackfire nova does UNSPEAKABLE things to a zombie of
a gorgeous silver-haired elf!
The oppressive force of the Archmage of Eternal Night's spell rolls over you in an
enervating wave.
The Archmage of Eternal Night's blackfire nova is powerless against you.

Zombies aren't immune to negative damage.