Dexter, Eastern Loreweaver

Reach, Intimidate, Trample, Vigilance
This creature enters with 10-{x} slumber counters on it. This creature's power & toughness is equal to the amount of world building counters you control. When it attacks, choose one of the following:
•Add world building counters equal to the amount of creatures, this ability cannot be used twice.
•Untap target creature.
•Put target opponent spell in graveyard into exile.