Staff of the Letter Magus is a uncommon Artifact card from Unstable (UST), collector number 159. Current market price: $0.18 (foil $0.46), TCGplayer market prices via Scryfall.
As this artifact enters, choose a consonant other than N, R, S, or T. Whenever a player casts a spell, you gain 1 life for each time the chosen letter appears in that spell's name.