Herkus is a druid who was transformed into a squirrel through a poisoned tea given to him by Demetria.
Hippofilius carried around Herkus as a squirrel until he could be healed at the Temple of the Five in Mytros. For this, Herkus swore an Oath of Service to him for a future, unspecified, deed. Hippofillius called upon this oath just a few days later, asking that he protect the freed Minotaurs from the Slave Market on their way to Pamplaxia.
Though Herkus has not stated it explicitly, conversations with him indicate that he supports the Titans right to rule.