Note: If you are in my gaming group (Ron, Brian, Ely, or Ray!) do not read this. Not for your eyes! Secrets revealed!
This is a sub-plot in my ongoing campaign, originally it was just my "slice" of the SG pie, but now that I'm main SG I am folding it into the overall plot, but that's another story. Wondering what everyone thinks, and if you like it feel free to use any ideas.
The players are aware of an isolated, wooded hill that is home to a very old pagan graveyard, still tended by a warped family I've named the Barrow family. It is essentially a pocket of paganism left alone by the rest of the world so far (in the saga we're on the edge of the Black Forest and it is very close as well). The Barrows essentially accept the remains of the few pagans that cling to the old ways, and they also take the remains of executed criminals and other non-Christians (gypsies and Jews who aren't claimed by kin, etc.). The hill actually has a number of separate graveyards on it, used at various times throughout history and closed when they get full, but that's of only secondary importance.
The top of the hill is a horseshoe-shaped ridge with a wide grassy meadow enclosed in the arms of the high ground. There are three concentric rings of old barrows: the outermost ring is 13 barrows, the middle ring is 7, and the innermost ring is 3. In the center of that is a massive, unusually warped tree that appears to be numerous different species of tree all growing together. All over the bark of this tree appear numerous "faces".
What the players don't know yet is that this is the remains of an old battle between Romans and Germanic tribes. A group of 4 Mercurian wizards with an army escort were taking a powerful written spell into the Black Forest to a garrison, as the Romans were fighting one of many heated rebellions at the time and the Mercurians stationed there needed a "last ditch" spell in case they were overrun. Instead, this group was ambushed and a running battle took place over several days, until the Romans made their way to this hilltop, there to make their last stand. At the time the ridge was completely circular, but a Roman spell blasted a section of it away (along with hundreds of Germans) leaving it in its present, horseshoe shape. More bitter fighting, and finally the Mercurians used the spell in their possession, more of a curse, really, as it transformed them into very powerful, but terrible revenants, except for the spellcasting "leader" who became a lich.
This nearly spelled doom for the Germans, but nine of their greatest sorcerors put their very souls into a potent spell that transformed all of them into a massive, magical tree and trapped the lich in a tomb of living wood and earth and magic. The three other revenants were overcome and they are buried in the 3 inner barrows, with magical rune-wards carved into their tomb seals. The ring of 7 barrows are the tombs of the 7 Germanic wizards who died sealing them in, and the outer ring are the 13 greatest heroes of the battle. The entire burial ground is essentially a spirit powered warding system, with the spirits of the 13 heroes and the 7 wizards providing the power that contains the 3 revenants and feeds magic energy to the Guardian Tree.
In my story a graverobber opens one of the 3 revenants' tombs, freeing it, and now it is working to free its evil master from the Guardian Tree. I am running this is a regio into the spirit-world; one magus already went into it via a fortunate twilight experience and actually talked to the Guardian Tree, but they still don't know the full story yet. What do you think?
Extra powerful spirit masters with a version of Wiz. Communion? Sounds about right here