People: The Conflict of Daemons and Demons
The Demon clan (which is set up with a variety of sub tribes) adopted the Daemons (even naming their clan after them in a fashion) to teach them their skills. They knew the humans to be the most skilled, disciplined, and knowledgeable. They found them worthy of tutelage. They taught the Daemons how to use demonic symbols in spells.

Many years later the Daemons had taken for granted the great trust that the Demons had placed in them and thought to double cross their educators. This double cross led to the near extinction of both tribes. The Demons will tell you one story while the Daemons will tell you another. Neither clan seems to have the full story on what exactly happened, nor are either willing to believe the truth of the matter.

Tensions run high these days between what remains of the clans, now mostly half-demons (and perhaps some full demons in deep hiding) and Daemons who will not admit their own heritage (perhaps to rid themselves of the stigma of their misunderstood magic. Daemon magic has become much more widely accepted since the decline of the clan and since the discovery of the Book of Daemonica the stigma associated with the practice has largely declined.

The tension may be overcome if one or both parties is in denial of their lineage or power, or simply does not care about such matters.