Im no Lost Caverns Limited expert, but the cycle of Hidden lands saw some play, and it's generally useful to have 1-2 caves in your deck
Plus, they're a thrilling pack-opening experience, providing the opportunity to snag multiple Rare cards or even a possible Booster Fun treatment
If a card that isn't a transforming double-faced card becomes a copy of a card with craft, it'll stay in exile if you activate the craft ability
Events You can earn Gems by playing Gem-reward events too
Niv-Mizzet, the Firemind is a bit worse, but they both do different things and love to hang out together
Its easy for a dedicated deck to enable it, and flash shenanigans even let you get card draw on your opponents turns