Early Life (spoilers for Seasons 1 - 3)
Donaar initially presented himself to the C Team as a highborn member of Dragonborn society, arriving in a driven cart and giving the assumption that he had a lot of money. However he also showed signs of immaturity and a superiority complex, calling other races "hairy monsters" and taking full credit for most of his team's achievements. The team then realize that he is actually only 19 years old, and is an exiled prince from the copper dragonborn kingdom of Jinaar.
In a comic released by Ryan Hartman and artist Nurse Normal, it is shown that Donaar was looked down on by certain members of his family, excluding his father the King and his elder brother Nase. When he was 9, their god Vars Melis went missing and his father slowly slipped into a coma, which the others blamed on Donaar. His brother Nase, who was to inherit the throne, disappeared and was assumed to have died. Donaar eventually left the upper city and lived in its slums for a time with a female dragonborn named Cathra. Donaar doesn't reveal this to his Team, only saying that he left Jinaar to search for his god, carrying his brother's cloak and sword with him.
Acquisitions Incorporated Career (Spoilers) 
It is unclear how Omin learned about Donaar's quest, but he saw an advantage in forming an alliance with dragons, and sent Donaar an invitation to come to Red Larch. Donaar was frustrated by the trials in the Test Market, losing his temper often. He was also attacked by an animated door, and mistook K'thriss for a vagrant in need of money. He was eventually accepted as a member in good standing of Acquisitions Incorporated, and given the role of Decisionist. His most famous double-vote was in choosing for the C Team to accept a gothic cart as their new mode of transportation.
At some point, Donaar and Walnut exchange career paths, with Donaar becoming a Documancer. They are eventually switched back, but Donaar's tail, which by unknown means has a sentience of its own and is nicknamed "Kevin", has retained some documancy skills. Donaar's family also appear to have knowledge of documancy, with Vars Melis himself being well practiced in the ways of the Fundamental Court. It was due to a contract Donaar and Vars Melis made to rescue a city destroyed by The Six that Donaar had to pay 30 years of his life, with Vars Melis implied to have also paid a price.
When having to improvise for a food critic's visit to the Dran and Courtier, Donaar made it sound like it was his establishment, and that it was now called the "Yum-Yum Hut". Somehow Omin caught wind of this and sold the brand name to interested buyers, and a branch actually sprung up in Triboar. Donaar quickly set the owner straight and took over.
Personal Life (Spoilers) 
Family and Personality
Despite his young age, Donaar is very nurturing; protecting and healing a dragonborn egg he had rescued from the goblins that he named "Eggy". This egg was eventually recovered by its mother, princess Sorsha(Saoirse?) of Scalla, and hatched into a female dragonborn who had imprinted on Donaar and went by the name Chronaar. Since dragonborn children require their bonded parent's influence to develop, Donaar agreed to take on a godfather-like role.
On meeting Oak Truestrike from Team B, Donaar's first impression was that he was "cool", contrary to Walnut being completely turned off by him. Donaar later recovered Oak's scalp after the latter had been killed, and was surprised to find Oak begin to regenerate a new body from it. Donaar again felt a close bond with someone he had "raised", and felt betrayed by his team when they had chosen to kill Oak for good. "Why is death always the first answer [with us]?" he asked them, for the first time showing that Donaar actually had higher morals than the rest of the group. Rosie admitted that he was right, and went to comfort him.
Donaar may have fathered other children, having agreed to help a Lizard King in the Shadow Realm who needed a royal heir. One possible descendent was named Kuipid, following the reindeer naming tradition. A child who resembled Donaar who said his name was Dalonnar also tried to lead him to his old acquaintance, Cathra.
Donaar's sister Pran played the documancy game taught by thier father, which inadvertently had the cost of recently also sending their mother into a coma. There may also have been a cost to her own soul or sanity, as she became power-hungry and began manipulating her family and Prince Shimmerscale. This triggered the Noble Knife to send Cathra to assassinate Pran, but Donnar stopped her from killing all versions of his sister, leaving behind a version that seemed more like her old self. With Pran's wedding to Shimmerscale cancelled, the citizenry of Jinaar were desperate for other forms of celebration, and Donaar reluctantly agreed to marry Cathra, while his brother Nase married Sorsha, and his parents renewed their vows.
The Jinarri believe in the dragon god Vars Melis, who speaks to the populace via messages passed on to the King, and grants power to his priests. Over time, this power began to fail. Donaar left home to search for their missing god, but to his surprise, Vars manifested inside Donaar during a battle with the evil goddess Tiamat, whose cult tried to summon her beneath the town of Red Larch (which henceforth became knows as 'the town that beat the dragon'). When the C Team went to space to fight the Sanguilith, the sentient god-prison pulled Vars out of Donaar. Donaar was reunited with his brother Nase, and together they struggled to free their god, who was ultimately released. Donaar was later surprised to learn that his sister Pran was betrothed to Prince Shimmerscale of Scalla, a known follower of Tiamat and the biological father of Chronaar. The Jinarri were told that Tiamat was the one who had freed Vars and that both returned in the form of a "unified goddess", which greatly upset the C Team.
It was later revealed that Vars Melis is actually an artificial god, created through the documancy of Donaar's ancestor, and sustained through rituals which the royal family perform and his ancestor's own life force. When the ancestor then tells the family that he is tired of his role and that one of them must take over, Donaar accepts the responsibility and sits on the dragon's throne. Although it is assumed that he has now merged fully with Vars, a fresh version of Donaar (still looking like his 19 year old self) appeared, but with an invisible spiritual thread linking him back to the holy mountain.
Physical Attributes and Notable Equipment 
Donaar's D&D Beyond sheet can be found here and his Idle Champions profile is here. He was bitten by a wearbear and acquired lycanthropy, but his tie to Vars Melis is implied to suppress his transformation, which he only managed to do once (although he intentionally spit in his Team's food to pass the curse to the rest of them). He therefore does not get the damage immunities of lycanthropy.
- Toothbrush - A large greatsword with a serrated edge; this weapon used to belong to Nase and was carried around by Donaar, who did not realize that the spirit of his brother was actually trapped inside it
- Floss - a whip
- Percival - an actual bejeweled toothbrush carried by Donaar
Ryan has said that the naming in Donaar's family follows a certain pattern.[4, 6] What is clear is that they are named after Santa and his reindeer as listed in "T'was the Night Before Christmas" by Clement Clark Moore. The royal family also have two first names (they all share the last name, 'Jinaar'). Donaar's summoned steed is a reindeer named Clarkmore, and his spirit guardians are also little reindeer.
- Sin’ter-Kla: the king, named after Santa Claus (Dutch spelling Sinterklaas)
- Joulu-Pu’kki: the queen, named after Santa Claus (Finnish spelling Joulupukki)
- Nase-Rote: referring to Rudolph's "red nose" (German spelling rote nase). He is the eldest sibling and was the presumed heir to the throne before he "died".
- Kåmit-Amor: named after Comet and Cupid - the god of love (amor). Young Donaar nicknames her "Kami"; she is the next eldest.
- Schlagur-Tänzer: named after Dasher and Dancer. Young Donaar nicknames him "Schlagy"
- Donaar-Blit'zen: named after both Donner and Blitzen. The words are also German for 'thunder' and 'lightning'
- Pran-Seren'vix: Donaar's little sister, described as a "bully", named after Prancer and Vixen
Ryan is actually working on a novel that tells Donaar's background story.
- Acquisitions Incorporated The "C" Team, "Franchise Opportunities" (S1 Ep1), https://youtu.be/ywZ0TcUh3l0
3. C Team S3E33, Crucible, Part 9
4. C Team S3E33, Crucible, Part 8
5. Acquisitions Inc, The “C” Team: Conflicted, by Robin Childs. YouTube.
6. "I Don't Get Donaar's Family's Naming Conventions" discussion on C Team Reddit.
7. Acq Inc: The "C" Team Live - PAX Unplugged 2017.
8. C Team S3E37, Crucible, Part 12; PAX Unplugged 2019