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The greatshell is a type of large crustacean-like creature, occupying many different environments on Roshar.


Greatshells have antennae, shells, and violet blood that smells like mold. Many greatshells are far larger than any crustacean should be able to grow. Roshar's low gravity, high oxygen atmosphere contributes to their great size.[1]


Greatshells have an integral and symbiotic relationship with a smoke-like spren (i.e., smokespren) without which they could not attain such a great size).[2] These spren also float out of a freshly killed chasmfiend's body. [3]

In order to survive with the science that Brandon built, almost all greatshells require some sort of spren to keep them from collapsing. These spren also accompany chasmfiends, skyeels, and anything else that should be heavier than it actually is.[4] Sailors call them luckspren. At the center of every greatshell is a massive, uncut gemstone called a gemheart. It is not clear whether the gemhearts actually function analogously to hearts.


  • Chasmfiends live inland, in the chasms of the Shattered Plains. They can grow as large as fifty feet tall, have massive claws, an incredibly thick, stone-like carapace, and mouths full of barbed mandibles. They have large gemhearts.[5]
  • Lanceryn were the only known source of large gemhearts to the Alethi, before the discovery of chasmfiends. They died off during the scouring of Aimia.[6]
  • Chulls are common small shells.[7]
  • Yu-Nerig are aquatic greatshells in the depths off the coast of Marabethia.[8] They are known for their succulent flavor. Many of the Reshi Isles are not actually islands, but island-sized greatshells.[9]