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The Lost Caverns of Ixalan is Magic's take on the “Underground World” trope. It is not a traditional return set: R&D was making an underground set, and Ixalan felt like the best fit for it. It wasn’t the other way round. As such, it is not a mechanical return to the previous set. The set has Dinosaurs, Merfolk, Pirates, and Vampires, but it isn't factioned or particularly typal. Thematically, it is more of an action/adventure set.

The Lost Caverns of Ixalan contains 291 regular cards (108 commons, 92 uncommons, 64 rares, 22 mythic rares, 5 basic lands), and includes randomly inserted traditional foil versions of all cards. The regular cards include 5 full-art "Core" basic lands (#286-291). Alternate card frames have a different card number than the original version. The mural-like "Legends of Ixalan" showcase cards are #292-313, and cards with the Gods of Ixalan treatment are #314-319. Borderless Dinosaurs are #320-332 while "Borderless Oltec" cards are #333-346. The Borderless Restless Lands are #347-351, #352 is the borderless Quintorius and extended art cards are #353-392. Bundle basic lands are #393-402. Promo cards are numbered #403-409. The Neon Ink versions of Cavern of Souls are #410a-410f.