Prince Ansom's forces included his own Jetstone tribe, other Royal-ruled tribes, various tribes of Elves, and Marbits. His goal was to conquer Stanley's last remaining city and put an end to him. As the story began, he anticipated an easy victory, given the massive numerical superiority of his forces and Stanley's history of inept leadership.
His publicly declared reason for leading the fight was to rid the world of Stanley's "great evil" (several of the other coalition members have been attacked by Stanley, though Jetstone itself has suffered only minor skirmishes with him prior to the current war). However, Vinny Doombats suspected that his real motivation is that he disliked Stanley's rise from common infantry unit to Overlord. Ansom would deflect the question rather than answer it, giving the impression that the suspicion was correct.
Ansom strongly believed in the special status of royalty and nobility. This manifests as a strong sense of noblesse oblige and personal courage. On the other hand, it fed his tendency toward overconfidence and caused him to underestimate his "inferiors".
He possessed, but was not attuned to, the Arkenpliers. Even unattuned, they have the ability to "turn most uncroaked to dust"; it is not known what abilities they would manifest in the hands of an attuned wielder.