Ehhhh nowhere did it say she was more powerful than anyone. It said she "could" surpass Sargeras, but that was simply Eonar's opinion.
Also Sargeras only wants to destroy Azeroth not convert. He's destroyed plenty of others with no indication of wanting to convert them.
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I mean if she does we all die.
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Source? Anything I see basically tells the normal history of it that we already knew.
I thought Sargaras himself was a Dark Titan. Was that Retconed?
I understand that but listen to the VO files again, think of the pattern Blizzard takes when introducing new content. N'Zoth is pretty confident that she/it was almost out of the Prison and the the last of the Old Gods left to do the job.
We go into Pandaria to stop the Mogu who were empowered by Titan and Sha powers and Garrosh becomes corrupted by the Sha. We go into Draenor to stop the Iron Horde who are empowered first by Primal Elements then Fel then we fight Gul'Dan who becomes even more Fel Empowered. Wouldn't it just be funny coincidence that the final boss that was expected at the beginning of the Expansion isn't the one one the Box Art ... again. I'm not saying it has to be a corrupted Azeroth but it could always be a possibility