Rothga, Bonded Engulfer 
Legendary Creature — Phyrexian Beast
Trample When Rothga, Bonded Engulfer enters, you get a one-time boon with "When you cast a creature spell, it perpetually gets +X/+X, where X is its power."
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyNOT LEGALvintageNOT LEGALcommanderNOT LEGAL