Astromancer Arwyn (specifically 7/7) is currently unbeatable due to the changes recently made to Sorcerer’s Apprentice stopping you from reducing a card’s cost below (1) (in this case Arcane Intellect). This effect seems to also be active in the aforementioned puzzle even though being nowhere present on the card text in game. I’m unsure if any other of the puzzles are affected by any recent card changes (apart from lethal which I tested fully) but as it stands this one is not doable currently.