Nyssa of Traken is a rare Legendary Creature — Human Scientist card from Doctor Who (WHO), collector number 366. Current market price: $0.49 (foil $0.49), TCGplayer market prices via Scryfall.
You have no maximum hand size. Sonic Booster — Whenever Nyssa of Traken attacks, sacrifice any number of artifacts. When you sacrifice one or more artifacts this way, tap up to that many target creatures and draw that many cards. Doctor's companion (You can have two commanders if the other is the Doctor.)