Mahito, Beyond Death's Mirror

When you cast this spell and at the beginning of your upkeep, put a soul counter on target creature and Mahito.
Creatures with soul counters on them are humans in addition to their other types.
Mahito's power and toughness are each equal to the number of humans your opponents control.
Whenever a nontoken human dies, create a 1/1 black human token. Put a soul counter on it and Mahito.
Remove a soul counter from a creature:
-Target human gets -X/-X or +X/+X until end of turn, where X is the number of s