Morska, Undersea Sleuth is a mythic Legendary Creature — Vedalken Fish Detective card from Murders at Karlov Manor Commander (MKC), collector number 317. Current market price: $0.69 (foil $2.10), TCGplayer market prices via Scryfall.
You have no maximum hand size. At the beginning of your upkeep, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Whenever you draw your second card each turn, put two +1/+1 counters on Morska.