Bellator was a Time Lord.
He went to the Tower of Silent Memory to select his next and last incarnation's form, but it went wrong and he was killed, alongside six other Time Lords who had died in the same way that very day. This was later revealed to be the work of Fey Truscott-Sade, who, after being manipulated by Alexander Truscott, sabotaged the Time Lords’ regeneration code as part of a plan to ruin them. However, she initally believed that this was not her doing, but that of the Absence, who the Twelfth Doctor later proved was never actually real. Prior to this, Fey showed the Doctor footage of his death as she explained her plans to him, leaving him horrified. (COMIC: The Clockwise War)