He is the Lord Regent and former Spymaster of Dunwall who masterminds the death of Empress Jessamine Kaldwin, as well as the coup to seize control of Dunwall, which he succeeds in doing.
His rule is both oppressive and corrupt, which causes the people of Dunwall to begin to rebel. This dissatisfaction becomes more pronounced as Corvo eliminates Burrows' allies, cutting off his funding and crippling his ability to pay the City Watch. Burrows, however, blames the city's problems on the Empress, and on the laziness and disorder of the common folk. Corvo is tasked with assassinating him during the mission, Return to the Tower.
Before taking on the role of Lord Regent, Burrows was formerly the Royal Spymaster. As such, he worked with great impunity and little oversight, staging campaigns of espionage against the gangs of Dunwall (including the Bottle Street Gang) and making plans outside even the Empress' knowledge.
The Heart reveals that Burrows suffers from a compulsive need to have everything in order, a characteristic which is also shown in his field notes. Several years prior to the events of Dishonored, he began internal investigations to root out traitors within Dunwall's government, which put him at odds with the Empress; he claims that "her very nature as a trusting person" blinded her to the work of traitors that "must" move among them.
Burrows is distressed by what he perceives to be a lack of concern on the Empress' part for security and order, saying "[she] would rather spend her time with the Royal Protector." He also disapproves of how she parents Emily, saying that the child is undisciplined and spoiled, and that "every moment spent at play is a moment wasted."
An audiograph stolen from Burrows' safe during the Return to the Tower mission (and linked to Burrows' non-lethal elimination therein) reveals that the rat plague was caused by Burrows himself: he and his retinue introduced infected rats from the Pandyssian continent into the poorest quarters of Dunwall to eradicate poverty by eliminating the poor. However, the plague quickly spiraled out of control.
Burrows feared that his scheming would be discovered by the Empress, who had ordered him to investigate the matter for evidence of foul play. He then commissioned the assassin Daud to eliminate her. Thereafter, he takes charge of the Empire as Lord Regent in order to steer it toward what he envisions as Gristol's grand, shining future.
Lady Boyle is his mistress, and based on his writings, has been for several years. She is also his financial backer, though whether this preceded his rise to Regency is unknown. He is deeply fond of her, spending his limited off-time in her company, and based on notes found in Dunwall Tower, is highly distressed by her fate.