Mana Conference is a uncommon Land card from Unknown Event (UNK), collector number UL01a. Current market price: $40.98, TCGplayer market prices via Scryfall.
When Mana Conference enters the battlefield, each player secretly chooses a basic land type, then those choices are revealed. Mana Conference gains each basic land type that received at least one vote. (Basic land types are Plains, Island, Swamp, Mountain, and Forest.)