User blog comment:GotMilk5101520/Silver Backstory & Tartarus and the Tower of Heaven/@comment-24066070-20140603140216

The cult who build the ToH may or may not have been in league with any of the Balam Alliance members.

If they were, then the cult had been told a false story that Zeref needed to be revived, since I bet that every Guild of the Balam Alliance knew that Zeref wasn't dead.

Precht knew that Zeref needed to be awoken from his "slumber", Tartarus more than likely knew he was alive as well due to them being his creations and considering the fact that Brain was a knowledge freak who interacted with the other Balam members, it isn't too hard to assume he was aware of the fact that Zeref was never dead to begin with.

Even if the cult wasn't in league with Balam, it is still a fact that at least 2 sides of the Balam Alliance used the ToH for their own convenience.

Brain recruited his OS members and Precht used the ToH in a plan to distract the MC.

If the cult was working directly under the orders of at least one Guild in the Balam Alliance, my bet would be on OS, because Brain possibly planned to recruit the kids with powerful magical talent among those gathered by the cult.

If it was really Tartarus who ordered/manipulated them to build the ToH, it may have been an experiment to revive E.N.D. rather than Zeref, but they possibly abondoned it for some reason.

Concerning Silver, it could be he was once the ultimate Take Over mage who only met his downfall when he tried to absorb Deliora and ended up being corrupted by Deliora.

What if Ur was the "original" Ice Devil Slayer who went to stop Deliora and her defeating Deliora allowed the fusion of Silver and Deliora to escape its berserker state and use TO on Ur's Ice Devil Slayer power? As soon as Tartarus brought Silver/Deliora to Hell's Core, he was permanently turned Devil with access to Ur's IDS. If Silver was once a TO mage, it would be he's Elfman's father and the grave he visited might belong to the mother of the Strauss siblings. His hatred for Gray could be due to the fact he recognizes him as Ur's student and therefore he fears Gray may be one of the people capable of defeating his current demon form. I wouldn't know how he knows Natsu. Oh well, I may be trying too hard to find an alternative to the nearly inevitable "Gray is Silver's son"