Enchant creature When Claustrophobia enters the battlefield, tap enchanted creature. Enchanted creature doesn't untap during its controller's untap step.
At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If an instant or sorcery card is revealed this way, transform Delver of Secrets.
"Unfortunately, all my test animals have died or escaped, so I shall be the final subject. I feel no fear. This is a momentous night." —Laboratory notes, final entry
"Garl, adjust the slurry dispensers. Garl, fetch more corpses. Garl, quit crying and give me your brain tissue. If he doesn't stop being so rude, I'm quitting."
Defender {1}{U}: Put a hatchling counter on Ludevic's Test Subject. Then if there are five or more hatchling counters on it, remove all of them and transform it.
Flying {1}{U}: Mirror-Mad Phantasm's owner shuffles it into their library. If that player does, they reveal cards from the top of that library until a card named Mirror-Mad Phantasm is revealed. The player puts that card onto the battlefield and all other cards revealed this way into their graveyard.