Summon: Leviathan

The Saga chassis turns a summon spell into a two-turn tempo swing that only sea creatures survive. Chapter I is a one-sided bounce that reads its exceptions off a specific list (Kraken, Leviathan, Merfolk, Octopus, Serpent), so the fallout depends entirely on how the board is built: a mono-blue tribal deck watches its own team stay put while everything else goes back to hand, and a stray non-serpent in your own ranks pays the same tax as the opponent's. That asymmetry is the whole point, a payoff engineered to reward committing to the aquatic tribes rather than splashing them. The back half of the Saga converts that tempo lead into a draw engine: for one turn each, any qualifying attacker cashes an attack into a card, rewarding a wide board over a single fatty. The 6/6 body is the tension the design has to solve, since the Saga sacrifices itself after chapter III and leaves nothing behind unless you find a way to keep it around. Ward matters less as a shield for the body than as insurance on the payoff: the rewards arrive over successive draw steps, so removing the enchantment before those later chapters resolve steals the second half of the deal, and the ward makes an opponent pay for that theft. The card wants a very particular deck, and it pays that deck in tempo now and cards later before quietly disappearing.