Watcher of Hours is a rare Creature — Sphinx card from Murders at Karlov Manor Commander (MKC), collector number 335. Current market price: $0.32, TCGplayer market prices via Scryfall.
Flying, ward {3} Whenever you remove a time counter from this card while it's exiled, surveil 1. Suspend 6—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)