Embermouth Sentinel is a common Artifact Creature — Chimera card from Tarkir: Dragonstorm (TDM), collector number 242. Current market price: $0.14 (foil $0.23), TCGplayer market prices via Scryfall.
When this creature enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top. If you control a Dragon, put that card onto the battlefield tapped instead.