Icy Prison

In Commander, Icy Prison is a niche inclusion — the island tax is real in four-player games where you need the enchantment to stick for multiple turns, and most blue decks would rather run Imprisoned in the Moon or Reality Acid for set-and-forget control. Legacy and Vintage allow it but ignore it; cheaper and cleaner answers exist at every point on the curve. Pauper is where Icy Prison gets a second look, since the card pool is shallow enough that zero-mana interaction with a recoverable downside is worth evaluating, especially in tempo builds that can replay the enchantment. Oathbreaker mirrors the Commander read — blink your signature spell, and the cost structure suddenly looks very different.