Guile

Commander is where Guile actually lives — the multiplayer table gives you a constant stream of spells to steal, and the indestructible recursion clause means removal barely slows it down. In Legacy and Vintage, six mana is a non-starter against fast blue decks that would rather run something that costs one or two, and the effect is win-more at a cost that concedes the early game entirely. Modern is technically legal but practically the same story — the format moves too fast for a six-drop that needs other counterspells to function. Stick to Commander, where the slow-roll power of repeatedly stealing high-impact spells off the stack is at its most devastating.