User blog comment:FairyRaven/Fairy Tail Chapter 390: The Story of a Boy, Review and Commentary/@comment-4829046-20140627085629/@comment-1776824-20140627091953

Here is how I look at it:

Deliora killed Silver and liked his body, and took it for his own (possibly back to Tartarus so it could be patched up beforehand). Gray went to train with Ur during this time, and was gone for x-amount of whatever. Deliora reappeared, yet again in his demon form, but this time to just wreak havoc, as he already had a body to use. This means that Deliora can take whatever human body he desires and use it as his own, and that it becomes his default appearance because, as well as that he can shift in and out of human and demon forms at will. Now, if Silver's body became his default body, then when he actually died in the Galuna Island arc, it only makes sense that being a member of Tartarus before all this, he would be revived in Hell's Core in the body of Silver Fullbuster, instead of in his own goddamn huge body.