Bone Beast sounds like the best option.
It reconfigures its bones to free some bones to be combined with the addition
to form a new Bone Beast.
...actually, I was saying the stats could be 4|3 unupped and 5|3 upped.
Just BTW, if I went with death as this card's element, would Bone Beast be a good name?
So the Unupped would be a +2|8 growth[+2.45
] and the upgraded has a +3|8 growth[+3.45
].
So cost
Unupped:4(attack)+2.45(+1|8 growth)-1(Activation cost 2-3
)=5
Upgraded:5(attack)+3.45(+2|8 growth)-1(Activation cost 2-3
)-1.5(upgrade)=6
5
|6
cost for single use skill