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The Nomadic Warrior's Cookbook 15 is one of the many Key Items found throughout Elden Ring, sold by the Southern Aeonia Swamp Bank Nomadic Merchant in Caelid.
The Nomadic Warrior's Cookbook 15 is a Key Item Recipe Book that will unlock extra crafting recipes once you have obtained it.
This includes the following recipes:
Purchased From: The Nomadic Merchant stationed along the main Caelid Highway on the southern bank of the Swamp of Aeonia, just past the Map Stele. It is sold for 4,000 Runes.