Canoptek Tomb Sentinel

The trigger only fires on entering from a graveyard, and that single constraint is the whole design conversation. A four-mana 4/3 with vigilance reads as an unremarkable body, but the Exile Cannon reframes it as a spot-removal spell that whiffs when you cast it the ordinary way: the exile only happens when the card returns from the yard, not when it comes down from hand. That routing is what makes the Unearth clause do double duty. Paying the seven mana returns the Sentinel with haste for one swing before the end-step exile clears it, and because that return counts as entering from a graveyard, it fires the Cannon on the way in: exile a nonland permanent, swing, then vanish. The card is engineered to be a recursion payoff rather than a body you cast and forget, so any effect that puts it into the graveyard and then reanimates it (a sacrifice-and-recur loop, a mass reanimation spell, a targeted raise from the yard) converts a fair removal artifact into a repeatable exile engine. Cast from hand it does nothing but attack, and the design accepts that: the exile is priced to reward players who treat the graveyard as a launch pad and route the creature through it. The exile clause is the reason to bother; it answers indestructible permanents and recurring threats that a bounce or a destroy effect would leave standing.