OK, I figured it out: when I tried looking for Zixzax, he was standing next to a portal that's a bit off to the side, so I never saw him there. The imp whom I assumed was Zixzax hanging around the Weaver of Time was actually another imp dude I saved from the mines. So yeah, the rooms started opening, therefore problem solved. Thank you!
I did encounter a real bug, though: right after the cuscene revealing the Hunters', erm, past life, the can have a conversation and get trait points, but the first dialogue choice somehow counts for both of them, so they both get either Bold +1 or Cautious +1, regardless of what the second one said.
