A-Sewer Crocodile

The design idea is the interesting part: a 4/7 that survives combat trivially but does nothing to end games until you feed the graveyard, converting a defensive shell into a clock. The unblockable activation is not the reward for casting the crocodile; it is the reward for building a self-mill or spellslinger deck around it, where five distinct mana values pile up naturally and the reduction turns a clunky six-mana investment into a repeatable one-mana threat. That toughness carries the front half of the plan: the creature wants to sit back and block while your graveyard fills, then flip into an evasive finisher once the diversity condition is met. Most large blue creatures ask you to protect them; this one asks you to be patient, and the cost reduction is what pays that patience off. The Alchemy rebalance leaves that logic untouched: same graveyard threshold, same activation, just a point of toughness added to the back so the defensive stance holds up a turn longer while the reduction comes online. It is a build-around dressed as a blocker, and it only works if the deck around it is doing something other than casting a crocodile.