The Maelstrom is a common Plane — Alara card from Planechase Planes (OHOP), collector number 23. Current market price: $7.43, TCGplayer market prices via Scryfall.
When you planeswalk to The Maelstrom and at the beginning of your upkeep, you may reveal the top card of your library. If a permanent card is revealed this way, you may put it onto the battlefield. If you revealed a card but didn't put it onto the battlefield, put it on the bottom of your library. Whenever chaos ensues, return target permanent card from your graveyard to the battlefield.