Flying Gadrak can't attack unless you control four or more artifacts. At the beginning of your end step, create a Treasure token for each nontoken creature that died this turn. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Changeling (This card is every creature type.)

Haste (This creature can attack and {T} as soon as it comes under your control.) {1}: This creature can't be blocked this turn except by creatures with haste. {2}, {T}, Sacrifice this creature: You gain 3 life.

({T}: Add {R}.)