Half breeds and a Human
Shard of Dragon Soul
A magic Shard
This small stone can be used once per day to give the wielder a +10 bonus on any knowledge arcane, knowledge history or spell craft check
This item can be used in crafting, it has a magic level of 20
Using the darkest of rituals, a soul can be harvested and turned into solid form. To do such to a person creates a powerful magic item, doing such with a dragon is risky but the item would be of legendary power.