Routing portals to the Necroverse requires a basic understanding of the structure of the Necroverse, and its myriad levels. While the big book on Necro portals is in the process of editing, fortunately for my readers there are some simple rules which I will be graciously posting on this blog in the meantime.
So, first, let us look at the following diagram.
The majority of the time, your player characters are unlikely to come upon a Necro portal by chance alone. Unless, as a matter of course, your players are grave robbers or tomb raiders. No. For the most part your campaign will intentionally seek the entrance to the portal due to some key components in a quest.
Motives can be anything from grave robbery, unreasonable encounters with the undead, or kidnappings where shadows are rumored to carry off the mayor's numerous offspring to the city's graveyard, where they disappear, and are never seen again (or perhaps they're seen again as zombies or ghouls).
Finding the portal will depend on whether the portal is disguised, hidden, or literally invisible. Thus the means to discovering the portal entrance will vary by design.
Now, as to how the entire Necroverse (the quasi universe of the necromancer elite) is organized, this post details the routing of portals to the Underhalls. That is, the first level, or prequel to the Necroverse.
A portal in a graveyard will typically route to another graveyard, a cemetery, a shunned temple, or a foresaken place in nature. Let us say, for the sake of example, that your portal in the graveyard is disguised as a headstone over a grave. The magic user in the party casts a remove illusion spell. A dim light appears in the form of phantasmic mist over the headstone portal. The portal transports anyone who steps through it to an accursed asylum, long ago forsaken and abandoned.
Now, at this point there could be hours or days upon days of adventure just searching within the asylum for the necromancer who stole away with the crown of the King. The key portal on this map will route to the Underhalls.
Once within the Underhalls, players sense that space and time are disrupted. The long rows of catacombs stretch for miles in each direction at the threshold of a crossroad. Selecting the next portal, the one which leads to the innermost heart of the Necroverse (where the necropolis and other fouls realms coincide in an evil coalition against the world of the living), will require some thought and imagination.
The portal routing to the innermost heart of the Necroverse will reside in one of the corridors' chambers. Perhaps the sarcophagus of the pharaoh or the tomb of an ancient King will house the nefarious greater portal.
Keep us bookmarked for updates to the next 9PRPG book, Necro Portal.