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The Nomadic Warrior's Cookbook 16 is one of the many Key Items found throughout Elden Ring, sold by the Hermit Merchant in the Ainsel River.
The Nomadic Warrior's Cookbook 16 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 Hermit Merchant who resides deep in the Ainsel River under East Liurnia, in a large chamber below a giant hanging void creature. It is sold for 2,500 Runes.