User blog comment:FairyRaven/Fairy Tail Chapter 366: 1000 Souls, Review and Commentary/@comment-5598380-20140109212812/@comment-5598380-20140109224427

It also sounds like "Souls" are 'money' to Tartaros. First, Silver who said that he consumes souls of demons. Then Sayla who asked Elfman if he will sell her his soul. Then Franmalth.