The Pagan Temple is heavily guarded. Perhaps you'll manage to sneak inside if you pass yourself off as a sacrifice… Go to Priest Flauron and pretend you've fallen into his trap.
Go to Flauron
Target: Priest Flauron
The Temple of the Pagans is heavily guarded. You may be able to sneak in by disguising yourself as a live sacrifice for the Temple... Go to Flauron and pretend to be lured into his trap.
Head to Pagan Temple. On the way you'll see Flauron standing. Talk to him. Flauron will give you a fake pass to get into temple; it looks like a red rose.
Go in and walk to the end, past the guards, to the right, and look for the mirror[1]. Talk to it.
You're moved to Pagan Temple. Run to the door. A statue of a pagan woman stands by the door. Click it. The door opens. The red item (rose) you got earlier turns white.
Now you can open the first big door and the guards at the entrance won't mercilessly beat you any more, but you still can't open big door No. 2 — Chapel Door[2].
Notes
↑ The road to the mirror is broken in many places, so don't be afraid to jump into the gaps.
↑ To have full access to Pagan Temple, you need to complete the second part of the quest — Through the Gate Once More.