The End of Orcus?

At various places in the crypt you come across large runes, glowing faintly, etched into the floor of the passages. Rather than risk your own hides, Watt and Bill grab a zombie corpse and toss it onto the rune. A burst of necrotic energy assails you, and sends the weaker willed among you into a blind panic, fortunately short lived. Pressing further into the tunnels you are balked by yet another rune. And zombies spill from the corridors ahead. Nearby you hear heavy footfalls, and deep laughter.

With the zombies defeated easily, Mardeyrian peers cautiously into the next chamber. A vision of death, ten feet tall, wielding a mace in the shape of a skull and a shield that bears close resemblance to an iron door, stands in the chamber beyond. From the horns on its head and its ghastly visage, can this be anything but the demon prince of the undead himself? Undaunted, or at least with foolish bravery, you join battle. Tyr plumbs the depths of his memory, remembering the dark tomes he has seen that describe this demon. There is something bothering him, but it is some time before he recalls what it is.

The creature comes on strong, it's shield and mace brutally bludgeoning all who stand in its way. With a rain of blows it knocks Watt into a pit and dazes most of the party, insulting you all the while in its gravelly voice. Things look grim, but you battle back with your strongest attacks. Fencing furiously, Mardeyrian drives the thing to the brink of the pit in the centre of the room, and Watt bashes the creature into it. Tyr remembers.

"Orcus is supposed to have wings! And a tail! And... more skin, I think!" he shouts triumphantly. The Javelin of Kord flashes out, and burns through the creature's skull. So falls Morgrimm the Foul. The body crumples, but a small sphere of light rises from it, and flees through the wall. The threat is over, but its animating spark may have escaped. You prepare to rest, but Bill hushes everyone. In the passages behind you, stealthy footsteps may be heard approaching.