Kozilek's Sentinel

A 1/4 for two mana reads as a wall, and that defensive shell is the foundation the payoff sits on: four toughness keeps the drone alive through the turn you empty your hand, while every colorless cast pumps it before combat math is settled. The reward scales with how committed you are to colorless spells, which makes attacking power a function of your whole turn rather than its printed stats. The trigger fires on each cast, so a turn that strings together several colorless spells before combat can swing for far more than the body suggests; cast at instant speed (a colorless removal spell, an Eldrazi with flash) and the drone grows after blockers commit, turning a profitable block into a dead one. Devoid does no work for the trigger itself: a permanent's "whenever you cast" ability does not see the spell that became the permanent. What devoid signals instead is the deck this drone belongs to. It occupies the colorless-matters payoff slot, a marker that the surrounding spell count is high enough for the +1/+0 to stack repeatedly. It belongs to the wave of Eldrazi-era designs trying to make "colorless" a deckbuilding axis rather than just a property a card happens to have: inert filler in a fair red deck, a finisher in one that floods the board with colorless threats and turns a wall sideways for a number the printed line never promised.