Norn's Seedcore is a common Plane — New Phyrexia card from March of the Machine Commander (MOC), collector number 60. Current market price: $1.24, TCGplayer market prices via Scryfall.
When you planeswalk to Norn's Seedcore, chaos ensues. Whenever chaos ensues, reveal cards from the top of your planar deck until you reveal a plane card. Planeswalk to it, except don't planeswalk away from any plane. Put the rest of the revealed cards on the bottom of your planar deck in any order.