This looks like a free partial takeover. I'm not quite grasping what this is. You can grow fangs, a tail and only that? Like a hybrid bird?Snakeform: The user is able to partially transform their body into that of a snake. In Cockatrice’s case, he has a serpentine tail and can protrude and retract serpent fangs from his beak at will.
Venomancy.Description: The user lashes out with their serpent tail, sending a shower of poisoned scales across a 5m area centered at a point within 10m of him. Enemies in the scale barrage take 1 D-Rank damage and are afflicted with Venomancy.
I don't know what it is. But it sounds like a Debuff or a marker of some kind, which no D-ranked spell can preform. You need to remove that.