Board Thread:Questions and Answers/@comment-91.198.134.226-20130407092701/@comment-8505655-20130510121102

The thing about Aggregor is that he is supposed to be the most dangerous enemy Ben has fought, according to some announcement made around the time of the beginning of Ultimate Alien. Let's not get into an argument about who the best villain may be, but it makes sense that he could be; if his plan succeeded, he would be nearly omnipotent. (Mind you, this precedes Diagon, make of that what you will.)  Essentially, my point is that he would be a very easy villain to ruin. If he shows up with anything short of a master plan, it would basically be like demoting him. There may be a way to successfully feature him with making him a major element, but it seems risky.

Also, if he does appear, he will almost certainly have a shirt on.