Caeleb and I have spied Frick's forces in battle a few times, and we have identified three Champions fighting with them. They are an even more bizarre, mis-matched collection than Frick's new common units are.
One of them is a tough, respectable warrior on a par with many of the other Goblin Champions we know about, but who has seeral unique things about him. The most important is that he is the first missile-wielding Cave Goblin Champion we know of; he is pretty good with his javelins. Second, he acts rather mysteriously for a Goblin, keeping most of his face covered. Third, he is peculiarly hostile toward other Champions: he fights ferociously against them, and they in turn match his ferocity against him. The one Champion we saw trade blows with him told us he is called Dibs, but he couldn't tell us why it is "Dibs", and refused to talk about the reason for the hostility.
But while Dibs acts mysterious, another Champion truly is a mystery to us. We have seen Frick summon him to battle as quickly and easily as a Runt, and then he will usually just sit in place and cut himself, and after a while vanish. Baffling. Our best guess is that he is doing some sort of long-distance magic like Scagg does.
The third "Champion" is another fell but trained beast from the caves, like the "Eater" that follows Sneeks. But rather than a Mole Ogre, this one is an enormous bat. Its wings are too vestigial for it to fly, fortunately, because it fights well and is very tough, taking many wound without dying. The most disturbing thing about it is that whenever a nearby Goblin dies it gives a bone-chilling shriek, and soon afterward attacks with redoubled fury. Caeleb suspects that there is some kind of shamanistic bond between the bat and the troops, but I think it is the normal bond between an animal and its owners. Whatever the cause, the effect is something to be wary of.
That is all we know for now, and we leave it to you commanders to plan how to fight these new Cave Goblin forces. We will of course report anything more we learn.