Bluestone Behemoth

Other creatures you control with mana value less
than or equal to the number of +1/+1 counters
on Bluestone Behemoth have hexproof.
Evolve (Whenever a creature enters the battlefield
under your control, if that creature has greater power
or toughness than this creature, put a +1/+1 counter
on this creature.)
The bigger it gets, the easier it is to hide behind.