Custodian/ID

A custodian is a troll's lusus naturae companion.

Lusii choose troll charges of the same blood colour in the brooding caverns after the pupated trolls complete their trials. From then on, the troll and lusus and lifelong caretakers of each other. The custodial relationship is vital, and allowing one's lusus to die or be lost through other means is grounds for culling.