Archaeomancer's Map is a rare Artifact card from The List (PLST), collector number C21-12. Current market price: $5.45, TCGplayer market prices via Scryfall.
When this artifact enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle. Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.