Ulvenwald Mysteries is a uncommon Enchantment card from The List (PLST), collector number SOI-236. Current market price: $0.27, TCGplayer market prices via Scryfall.
Whenever a nontoken creature you control dies, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Whenever you sacrifice a Clue, create a 1/1 white Human Soldier creature token.