Thantis, the Warweaver

Thantis, the Warweaver is a Commander card through and through — the mandatory-attack trigger only generates real value when there are multiple opponents and boards full of creatures to punish. In Legacy and Vintage, where it's technically legal, it's a six-mana do-nothing against fast linear decks that will never build the kind of board state Thantis wants to exploit. Commander is the one format where Thantis earns its slot: three opponents means three boards forced into combat every turn, and each attack trigger stacks counters fast enough to turn Thantis into a lethal clock within a few rotations. Oathbreaker is the only other format worth considering, and only in creature-heavy pods where the forced-attack clause has real teeth.