underground sea mtg card Proxy Island Swamp. Underground Sea #C - #1

The only downside for Zareth is if you want to use its second ability, you have to somehow get it into your hand, which can be done with ninjutsu cards like Prosperous Thief, trading them back and forth from your hand

With Dramatic Reversal, Stella, and a mana rock, we can make infinite mana

Enablers: As with knight-tribal, there are tons of cards to support this theme

Famously banned in Commander since before the Rules Committee combined the banned as/banned in Commander lists, this 9-mana mass board wipe was considered an unfun interaction in Commander games since it effectively restarts the game

These are all fairly pricey due to their sheer scarcity, but Command Tower takes the top spot among them