Re: the Drangeon
The PCs would be profiteering adventurers, mostly. Maybe an organized guild that exploits, more than helping, the various duchies, marches and baronies. But the work would be hard, a single dungeon may take various expeditions, and attract the overlord's attention in the meantime, so sponsoring an expedition is a double-edged deal for the authorities.
The "drangeons" would be very few, and only generated by dragons of legendary sizes, and it would be almost impossible to find one "vacant". The overlords would be very old, most of them liches, but the magic power of the drangeon is strongly tied to the place, so those "drangeon keepers" would very rarely leave their lairs.
There would be strange gears around which this world moves, and one of the driving points of the campaign will be to find our what they are. As magic is limited, spellcasting characters will have to follow a couple special rules, but they will also be central to the development of the campaign.
By end of this week I'll be posting the link to the game, and it's almost certainly going to be D&D 5e.