Here's my idea, hope you like it
A fusion card is a card combined from two "parent" cards, below are the examples:
Life cycle:Permanent free(pillar)
each turn, generates 1 death and 1 life
Parent cards:Bone pillar and Emerald pillar.
This one's a metamorph, its element is none of its parent cards'.
Predator:Creature 0/3(5 life)
Devour:Destroy the target creature if its hp is less than Predator's hp.Predator gains +1/1
Scavenger:for every creature death, Predator gains +1/1
Parent cards:Otyugh (gravity) and Vulture (d347h)
As you can see, Predator's element is different from Otyugh's and Vulture's.