The text that appears right side up on the card defines the card's normal characteristics
All it needs is a creature with power 2 or less to ETB
Apex Devastator Apocalypse Hydra Goldvein Hydra Gyrus, Waker of Corpses Hooded Hydra Hydra Omnivore Hydroid Krasis Kalonian Hydra Khalni Hydra Polukranos, Unchained Polukranos, World Eater Primordial Hydra Progenitus Protean Hydra Savageborn Hydra Shivan Devastator Ulvenwald Hydra Zaxara, the Exemplary
You can later make its power and toughness equal to the sticker you put on another creature
Ezrim, Agency Chief Ezrim, Agency Chief is basically Dream Trawler with a BA in Criminal Justice
Since Urza just gave us an artifact creature matters build in The Brothers' War, with more colors and better abilities, that may not get as much play, but she is also ideal in the 99 of that brew as well