Umor reigns for only forty days in 766 and belongs to the Ukil clan, according to the Namelist of Bulgarian Rulers, which makes him a relative of the former rulers Vinekh and possibly Kormisosh.
The Byzantine sources indicate that his predecessor Sabin had entrusted Bulgaria to Umor, but give no details of his short reign or fate.
Some scholars speculate that he was a champion of the peace party like his discredited predecessor, and that he may have likewise fled to the Empire.
The Byzantine chronicler Patriarch Nikephoros records that Toktu, who succeeds Umor, was "a Bulgarian, and a brother of Bayan".
Although this suggests that Bayan was a man of some importance, nothing more is definitely known about Toktu's basis of support.
