Echo Storm

Echo Storm is a Commander card through and through — its copy count scales directly off commander casts, a mechanic that simply doesn't exist in Legacy or Vintage in any meaningful repetitive way. In those formats it's a legal curiosity that would almost never produce more than one copy, making it a strict downgrade to cards like Cackling Counterpart or Saheeli's Artistry. Commander is where Echo Storm earns its slot: high-cast-count commanders turn it into a one-card board state, and the instant speed makes it legitimately threatening as a response to a tapped-out opponent. Oathbreaker has the same commander-recasting logic and could support it in signature-spell builds, though the smaller card pool makes finding the right shell harder.