“Common or uncommon artifact creature that puts cards back in your library for two mana” seems to be a new staple.

• Transplant Theorist
• Phyrexian Archivist
• Hoverstone Pilgrim
• Tomb Trawler
• Barkform Harvester

I rarely play them or see them played. It’s true that a non-zero percentage of my draft games end in board stalls with one player milling out, and in theory I like the idea of having some insurance for those scenarios, but the cards are never impactful enough in any other situation. But this one might come the closest – a 4/4 flyer for 6 isn’t bad, and in Duskmourn it can also function as a Delirium hoser.