The throne of the Dead

This adventure is placed in the world of dungeons & dragons. In this scenario the demon Lord Orcus seeks to overthrow the goddess of the dead. He is a demon lord that controls a layer of the abyss known as Thanatos. He is in undead demonic sorcerer who raises the dead to do his bidding and he is very powerful. He has unleashed hordes of the undead across all the land. He is gathering as many souls as he can to serve him in the abyss once he siphons their souls he is repurposing their bodies with that of the undead he can control. He takes their souls and reanimates their bodies to do his bidding. His plan is destroy all the temples and all the places of tribute to the gods that they may lose their power and he may storm the celestials strongholds to overthrow the goddess of death that he may no longer be claimed by death and all that pass away automatically become his undead slaves