Ruin Guardian Hydreigon

Flying
Whenever Ruin Guardian Hydreigon enters the battlefield, each player mills X cards, then put a
+1/+1 counter on Ruin Guardian Hydreigon for
each artifact put into a graveyard this way.
Whenever you cast an artifact spell, you may
remove a counter from Ruin Guardian Hydreigon.
If you do, copy that spell. (Copy becomes a token)