It did not take the party long to arrive at the conclusion that they had been betrayed. Someone must have tipped off the demons to the location of their insertion point, and there was no doubt that this tip off and the resulting resistance had bought enough time to allow the Demon Princes to arrive on the field before the heroes could help to close the portals. Someone had betrayed them and this betrayal had led to the deaths of Bahamut and Davros (as well as a number of nameless soldiers) and the loss of Celestia itself.
However, there had been no one in the meeting room when they were planning the mission save for the party (including Kheldor), Dante, Davros, and Kat. And outside of the Situation Room, the only person who had known about the location of their insertion point had been Abilard Dorminus himself. The party brought him in for questioning immediately.
They quickly ascertained that Abilard had had no part in their betrayal. They then began a lengthy questioning and investigation process, involving no shortage of pocket dimensions. I’m going to skip out on some details here and cut to the chase.
After a THOROUGH investigation they determined that Belaren was their betrayer, Vantrag had been an accomplice, and a certain Succubus had been his handler. Then all hell broke loose. The succubus dominated Z in an effort to use him to escape, Belaren grabbed Kat to take as a hostage, and Vantrag lunged at Roberts, swords drawn. After a short and onesided battle (thanks to Robert’s impressive duel-wielding skills and Kheldors calm, cool actions with his hand-crossbow) the party subdued Belaren and Vantrag and freed Z from the succubus’ domination. They then imprisoned the two traitors and hatched a plan to determine if there were anymore moles in their organization. Kat, disguised as the Succubus, would free Belaren and follow with him to see if he attempted to contact or round up any other traitors.
Thanks to Kat being Kat, the plan misfired somewhat. While they learned that there were no more traitors (at least none that Belaren knew of) the tiefling ex-commander of the Red Sashes managed to escape, and the party missed out on their chance for vengeance. Additionally, they were shocked and deeply hurt by Vantrag’s betrayal. Instead of executing him to make an example, they elected to hold him as a prisoner instead.