Shipwreck Sentry

A 3/3 for two mana in blue is a body the color almost never gets to keep, and Defender is the price stapled to it. The wrinkle is how that tag comes off: not through equipping, not through a permanent unlock, but through a per-turn condition that has to be met again every combat you want to swing. This makes the Sentry a conditional attacker rather than a wall that occasionally forgets its job. On a turn you make a Treasure, cast a cheap artifact, or otherwise send one to the battlefield under your control, the Defender clause lifts and you have an above-rate blue beater; on a turn you do not, it reverts to a stat line that blocks well and nothing else. The condition keys on an artifact entering rather than an artifact you already control, which subtly favors replay and token generation over static board presence: a Treasure created and then spent for mana still counted when it arrived, so the enabler and the payoff can be the same card in the same turn. That places it among the creatures whose full aggression is rented turn by turn rather than owned, asking a deck to keep artifacts flowing rather than to build toward one big unlock. Without that flow it is a serviceable blocker; with it, the toughness that makes it a good wall also survives the combats it chooses to enter.