Adrestia

The design conceit is a Vehicle that pays you for staying in-flavor. Any creature can turn the key for the price of one, but the attack trigger only fires when an Assassin crewed it, and the reward pairs a card with a temporary type change that makes the ship itself an Assassin until end of turn. That rider is the clever bit: once the trigger resolves, Adrestia counts itself toward any board-wide Assassin trigger, briefly widening a go-wide tribal board by one. The window is deliberately narrow, though. The change reverts at end of turn, so by the next combat the ship is a non-creature artifact again and can never bootstrap its own crew for a future swing; you still need a live Assassin to unlock the draw each turn. It also has no vigilance, so attacking taps it out: once it swings, it cannot itself pay a later "tap an Assassin" cost or crew a second Vehicle that turn. The islandwalk is a period detail dressed as an ability, a naval vessel slipping past anyone defending an Island coast, and it hands the card an evasion floor independent of the tribal engine. What holds it together is how trivially cheap Crew 1 is: a four-power body that converts any spare one-power Assassin into repeatable card advantage and damage that slips past Island defenders, without the tap-down tax heavier Vehicles demand. It wants a board of small, cheap Assassins to feed it, which is precisely the shell it was built to reward.