Interesting. I like that it adds a thematic effect onto the poison. Do you have a name in mind for the ability?
It does break the mold of venomous creatures a bit in that the effect changes when upgraded rather than giving it a stat boost. This may work out ok, however, since the upped meta will have access to chaos power to compensate.
It would be very ugly indeed if you gave it a
twin. It would give an interesting twist to disco-hole decks... Honestly I would like it better that way since there are more counters to creatures then there are for spells and permanents.