Relic's Roar

Cheap type-assignment is unusual territory for blue, and the split target (artifact or creature) is what lets this one moonlight in two plans at once. Point it at your own token or Treasure to conjure a 4/3 attacker out of nothing, or point it at an opposing blocker to blank its combat math by resetting its base power and toughness in the middle of a block. The Dinosaur type is not window dressing: in a deck built around that creature type, turning any legal target into one lights up your board-based tribal payoffs, and it slips into any window where blue can hold up a single mana. What keeps the effect in check is the "until end of turn" clock paired with the flat 4/3 floor: nothing is permanently upgraded, and setting a base of 4/3 can shrink a genuinely large threat as easily as it grows a small one, so this works as a tempo lever rather than a stat engine. Folding a combat trick, a token-into-beater conversion, and a tribal enabler into the same one-mana instant is how it earns its slot, and because it's an ordinary instant with all its targeting locked in on cast, both players get their chance to respond before it resolves. The versatility lives in the deckbuilding, not in ambushing an unwilling opponent.