Board Thread:Questions and Answers/@comment-32173189-20171227234730/@comment-78.194.252.210-20171228115341

Heroic Spirits themselves exist in the Throne of Heroes, that reside in Akasha. So when you invoke a servant, it's the aspect known in your dimension that is called and come.

Heroic Spirits can be considered a merge of all, but not the servants themselves that are only "an aspect".