With regards to Orcus's CR - I think the GM told us he is a 22. He was using stats from Hordes of the Abyss, a book I don't own. However, the GM has been known to mix up critter stats on the same page (we had to fight a force/prismatic dragon once, because the GM kept reading the stat block for one and the special abilities for the other). Also, every member of the party has an epic weapon (well, the dragon shaman didn't get his until we killed Orcus - we think the mace is probably his now) or item (in the case of the archivist). They gave really potent advantages to the warmage & the fighter, at least. That really only got us TO Orcus. The rest was our own stupidity/audacity..
With regards to why we were "picking on Orcus" - he was doing a ritual that would kill our characters as soon as it was completed - so far as we knew, we'd just drop dead, no saves, no other way to avoid it. So we had to get into his tower to disrupt it - not my fault his tower only had 4 rooms and he was doing the ritual in his throne room.
We don't actually know whether we killed him, or the Goddess for that matter, in character. Personally, my character (archivist) is assuming Orcus was only stunned, or that what we encountered was an avatar, and we sure left in a hurry, just in case. My character is also going to take up the worship of said sacrificial goddess. I may have to find a death-ward item, just in case..
