Skeleton and mummy should be allowed for this event. While they do not have actives, their passives require time quanta. Ghost of the past should also be allowed, as well as nightmare and voodoo doll. I also think you should allow for one spell from each element: nightmare, plague, rage potion, basilisk blood, momentum, rewind, purify, mitosis, the mass dive air card, twin universe, mutation, and holy light. Said cards synergize well with other elements (in some cases they are counter-synergies).
Also, I have a feeling mind flayers will be a tad OP in this format... graboids could have been, but with the lack of earth/time creatures fit for rushing, a deck around them probably won't be too great.
Wrong. They need time quanta to become another creature, and spells aren't even allowed on the first place. On second place, their Passive ability costs no quanta at all. You need to use it.
duo deck has been created to by-pass this problem
We don't are working on how you bypass the problem, we're working on how it isn't a active ability and nothing you do will change that.. Unless you're zanz.
Shouldn't Fireflies be allowed?
I know we have Firefly Queens, but Firefly's ability refers to another element 8)
The main point of this is to have abilities that are from the other elements. If you wanted to allow all the abilities, we could go with Dragonfly, Fate Egg, Fire Spirit, Arctic Squid, Shrieker, etc;.