This suggestion is more about flavour than fundamental changes to gameplay. I'd propose additional Shadow/Animus abilities to incorporate supernatural creatures from other cultures.
Shadow / Animus of the Jaguar - Originating from Olmec (and Maya / Aztec) mythology. For speed of development I'd suggest that these be direct copies of the Wolf abilities with the word Jaguar substituted.
Scream of the Jaguar - A copy of Howl but bringing a single Jaguar to the party.
Shadow / Animus of the Serpent - Originating from Indian mythology of Nagas. Shadow form would have no access to inventory or interactions, ability to slide under doors, move through water tiles at 1/2 AP per tile, gain Enhanced Senses and have a 6 damage Piercing bite that delivers Minor Venom (Poison). Animus form would remove the inventory and interaction restrictions, add +2 damage to HTH and Melee attacks and bite delivers Major Venom (twice the damage of Minor Posion).
Call of the Serpent - A copy of Howl that brings a giant Python to the aid of the summoner. Stats TBC but suggestion would be to have a crushing Impact attack that delivers the Entangled status effect (c.f. Shocked).