Xenoth, All Consuming

When Xenoth, All Consuming enters the battlefield or attacks, you may sacrifice another creature. If you do, attach the sacrificed creature
underneath Xenoth, this counts as a mutation.
Xenoth, All Consuming gets +X power, where
X is the combined power of all creatures under
Xenoth and gets and +Y toughness, where Y is
the combined toughness of all creatures under
Xenoth.