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The Ancient Dragon Apostle's Cookbook 3 is one of the many Key Items found throughout Elden Ring, found at the Cathedral of Dragon Communion in Caelid.
The Ancient Dragon Apostle's Cookbook 3 is a Key Item Recipe Book that will unlock extra crafting recipes once you have obtained it.
This includes the following recipes:
This item can be found at the Cathedral of Dragon Communion located in the south part of the Caelid region, just off the main highway and guarded by a large dragon, Decaying Ekzykes, as well as a few Banished Knights that patrol the ruined cathedral.