Board Thread:Questions and Answers/@comment-5420712-20140119142725/@comment-24085460-20140120123554

Lord Kisin wrote:

Tl;dr

We have Elder Demons that serve as Lords of the Race, who each have their followers bound to them by contract.

This pretty much sums it up, I reckon. Working on this theory, it would make sense that the Kal'Gerion are a group of demons contracted to serve Kal'Ger as opposed to, for instance, Thammaron. It's likely that what makes Kal'Ger stand out is that he is so phenomenally powerful without actually being an Elder Demon himself (unless I'm missing something). This is represented in-game by him having the highest combat level (in his full version) of anything in RS. I think the idea is that he's supposed to surpass beings like the mahjarrat and even Nex. It's not surprising, given all this, that an entire army of demons choose to serve him.