Chaotic Aether is a common Phenomenon card from Planechase Anthology Planes (OPCA), collector number 1. Current market price: $0.95, TCGplayer market prices via Scryfall.
When you encounter Chaotic Aether, each blank roll of the planar die is a {CHAOS} roll until a player planeswalks away from a plane. (Then planeswalk away from this phenomenon.)