Traitor #1: Lord Lorenz
Lord Lorenz was a nobleman with a house in Largos. In Interlude I, he kidnapped Lady Verina, the daughter of the Baron of Largos, and fled downriver to Tononir before cutting across the badlands to a shrine with a gate in it to the Interplanar Hub.
Within a stone’s throw of the shrine, he was caught by the Sol Knight novices and cut down.
Traitor #2: Azhelm Arajoel, Retired Mercenary Captain
Azhelm joined the group in Antares at the beginning of the campaign, hooking the novices into the 10,000gp reward for the capture of White-Eye. Azhelm showed his darker side when he proposed destroying the orc slaves at Largos to deny White-Eye his prize. He killed at least a dozen of them. After the battle, he persuaded the novices to join him in going after the 12,000gp reward for the safe return of Lady Verina.
Possibly it was the opportunity for claiming a full 22,000gp for himself with no loose ends that was sufficient temptation for him to trap the novices in the Interplanar Hub. The kicker was that he grinned whilst doing so.