Ester had been planning to arrest both the guardians and Guardian Seekers in one go once all gathered in one place. Luckily for her, she was informed of where they'd be meeting, and used it to apprehend them quickly. Not only did this announce to the Xannioba the guardians were real, but that they should be considered criminals for their actions. The Guardian Seekers also had crimes to atone for, but were more a nuisance to Ester's grand plan.
Ester believes with her influence in the courts, position of power as representative of Filfier, and amassed forces from the deck and her following that she is the only one capable of taking out General Darc. With that in mind, in order to not split credit, she felt the need to remove loose ends from her plan. The Guardian Seekers were a victim of this cut, as Ester found them to not be as useful as her closer assets. As for the guardians themselves, they needed to be removed for their lack of efficiency in Ester's mind. She disagrees with their way of handling things, and refused to let them roam free in the chance they could take credit for defeating this legendary threat.
At the trial, there was little to be done. Though Ester was willing to be a fair judge over the matter, allowing herself to be bested in the law should there be a case, Lefnar was still able to persuade everyone of the antagonism that occurred on the adventures of the Guardian Seekers. Though some charges were not guilty, not all could be overlooked. Originally, Ester was going to let the group out of captivity after her success against Darc, but she couldn't overlooked being called weak by creatures undoubtedly beneath her. A battle will commence where the party will be given an opportunity to best Ester for freedom, though she seems confident her group is unbeatable.