I think a lot of the Orcus scandel is left up to personal interpretation.
Depending on what gaming system one is looking through at the time of questioning. For instance, I know little of the D&D history on Orcus, as my gaming group only meddles with D&D on our off seasons of gaming.
In the Palladium Fantasy realm... Orcus died at the hands of Rhurga, the Goddess of Truth, with the help of Demigorgon his supposed right hand man. Now his realm in the multiverse of Palladium was not in the Abyss but was in fact in a place called Hell which translates into the Abyss or even Savannah, Ga for the wanderers out there. His palace was on the 666th plane of Hell where there was no direct way to travel to it. So in order to travel to his particular hole in the ground, one had to travel through the other 665 levels of Hell just to pay him a visit.
We actually are ending up our 4 year campaign dealing with the Prince Orcus who has been trying to bring back the Old Ones of the Palladium Fantasy world. Which for those not informed on the Old Ones, are pretty much H.P. Lovecrafts monsters put into games.
Anyway, I will go back to lurking now.
*If I am wrong in any of my information just pass it off as someone who is bored at work and likes to hear himself type.