Mount Keralia is a common Plane — Regatha card from Planechase Anthology Planes (OPCA), collector number 52. Current market price: $2.88, TCGplayer market prices via Scryfall.
At the beginning of your end step, put a pressure counter on Mount Keralia. When you planeswalk away from Mount Keralia, it deals damage equal to the number of pressure counters on it to each creature and each planeswalker. Whenever chaos ensues, prevent all damage that planes named Mount Keralia would deal this game to permanents you control.