Rhiannon Matthias

Violet's best friend in Fourth Wing, bonded to Feirge.

Rhiannon Matthias is a first-year rider assigned to Fourth Wing alongside Violet Sorrengail, and she becomes Violet's best friend. She is bonded to Feirge, a green daggertail. Her signet is summoning (Wikipedia's character list calls it retrieval).

Quick Facts

Dragon: Feirge (green daggertail)
Wing: Fourth Wing

Facts from the source article.

In Fourth Wing

Rhiannon and Sawyer Henrick agree to help Violet with hand-to-hand combat if Violet tutors them in history, and she becomes close friends with Violet, Sawyer and Ridoc.

Later books

In Iron Flame, Xaden gives Violet a special dagger for defense on a trip to meet the gryphon fliers. When Varrish captures Violet on her return to Basgiath, Rhiannon uses her signet to hide that dagger. She also knows Violet is keeping secrets from her. In Onyx Storm, venin disguised as scribes get into the Basgiath keep, and Rhiannon, Violet and Ridoc defend Jack Barlowe's cell in the fight that follows.