Tiergan, also known as Granite, is a Telepath and Sophie's Mentor at Foxfire. Tiergan is an anagram of Granite, both having the same letters. He does not like being called Sir Tiergan, preferring just Tiergan after the memory break of Prentice and his resignation from his position as an Emissary. Tiergan adopted Prentice's son, Wylie Endal, after Prentice was sent to Exile and Wylie's mother, Cyrah, faded away. He doesn't like the Vacker family, but does help them when Alden's mind is broken. During Neverseen, Tiergan is revealed to be Granite, part of the Collective of the Black Swan.
Tiergan is described to have olive skin, shoulder-length pale blond hair, and dark blue eyes. It also states that he has a short ponytail on the back of his head. While his face holds youth, something ancient shines in his eyes. He is described as tall and thin, but a couple of inches shorter than Alden.
The name Tiergan is of Irish origin and it means "strong-willed."
- WYLIE (adoptive son)
Prentice and Tiergan were very close—so close that Tiergan was first in line to adopt Wylie before Wylie's actual family. When Prentice's mind was broken, Tiergan was full of grief and blamed Alden for the incident because Alden was the one who accused Prentice of rebellion.
- ALDEN (dislike but eventually respect)
Tiergan has a lot of anger towards Alden, blaming him for the loss of Prentice. He seems to gain more respect for Alden, however, after he finds Sophie. He also is able to get past his own feelings to help the Vacker family with the grief of the loss of Alden when his mind is broken.
- THE COUNCIL (dislike)
In Book 4: Neverseen it was revealed that Tiergan works on the Collective under the name Granite with Mr. Forkle and it was suggested that the two could be friends or relatively close seeing how the two are around one another more than their other fellow Collective members.