A good explanation of the demons of your world, though the first section is a little rough and needs to be reread.
Some is a little confusing:
Likewise, though the daimons will usually be a minor threat as they can't rejuvenate themselves in their home, some were originally powerful enough to be a significant threat in their time spent as a daimon.
So, even though they cannot recover from injury while on Atheus, they start off powerful enough to remain formidable for quite some time?
It would be interesting to see a king arise that held power not through his impotent army, and figurehead status, but through ties to the underworld. Blackmail, careful manoeuvring, intrigue. Keeping to the appearances of a lame duck, he would actually hold significant power. How the PC's play a role in this, perhaps they could give the impetus to change.
The Eclipse certainly makes this submission - the city as it was was a nice high-magic city, but not overly remarkable. The transformation into the war zone gives it a desperate air and like Gossamer said, having the PCs there when all hell breaks loose would make the greatest impact.
Well done! This would make a very interesting mini-campaign. Go to Comment
This could easily work in Urban fantasy, perhaps even more so.
Someone like Hannibal Lecter (sp?) would be the perfect owner of this item, found during his years as a grad student screening artefacts. No one ever found his fellow student who disappeared on the dig... Go to Comment
For a long-term plot, the spirit inside the box would want to get _out_. For a powerful necromancer, not having a physical body once he does so many not be that big a deal - many undead are non-corporeal. The trick would be how to get out without being drawn off to the afterlife and probably consignment to Hell or its equivalent.
Perhaps a plot could be an infernal being looking to collect the 'overdue' soul of the necromancer. Maybe even recruiting the PCs to this end.
As for why it is not more common - I'd say it could in fact be more common as making magic items by binding spirits within is a perfectly reasonable way to go.