[Zen]

Artifacts are fine as they are. There is no reason that anyone should lose an artifact if they have created it (outside of the good ol' fashioned, kill'm and take it method).

As far as suggestions go:

Unique summons on the other hand could have a chance of loyalty switching (or possible going BREZERK!) if they are summoned.

Something simple yet might add another dynamic could be 25 base chance modfied +/- 5% on the difference in main path of casting unit.

Thus an Ice Devil summoned by a 3 Blood Caster first, but if summoned by a 6 Blood Caster later would have a 40% chance of deserting their original summoner and heading to join more powerful blood mage.

Or a 6 Blood Caster casts it first, and a 4 Blood Caster tries to steal him away, he'd only have a 15% chance of taking away the ID.

This could work well for the Royalty and the Blood Summons. Then of course a 10% chance from the chance of Loyalty could cause the Devil/Elemental Royalty to "GO BREZERK" (4% chance with 40% and 1.5% with 15)