Bone Beast sounds like the best option.
It reconfigures its bones to free some bones to be combined with the addition
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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
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] and the upgraded has a +3|8 growth[+3.45
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].
So cost
Unupped:4(attack)+2.45(+1|8 growth)-1(Activation cost 2-3
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)=5
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Upgraded:5(attack)+3.45(+2|8 growth)-1(Activation cost 2-3
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)-1.5(upgrade)=6
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5
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|6
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cost for single use skill