Gift of Change

Pick 1 enemy unit within 18'' of the caster and
visible to them.
That unit suffers a number of mortal wounds
equal to the Gift of Change value shown on the
caster's damage table.
If any models were slain by this spell, before
removing the first slain model, you can add a
Tzeentch Chaos Spawn to your army
and set it up within 3'' of the slain model's unit.