Primordial Dungeon Core:
Can possess any form and has the ability to place all other Dungeon Cores under its control. Its blood has the ability of polymerforzation and can turn into anything the Primordial Dungeon Core has the power to create.
I say just start righting and see were it takes you. Just make sure the stuff you come up with makes some amount of since. Also make sure to reread it so you don't contradict yourself.