Sleepy was a sworn member of the Black Company who joined the Company after the Liberator led the legions of Taglios in a successful liberation of the city of Dejagore and slaying the Shadowmaster known as Stormshadow.
Sleepy eventually gained the friendship and favor of the Company standard-bearer and annalist, Murgen, during the ensuing Siege of Dejagore. Once Croaker relieved the siege, Sleepy became Murgen's choice to succeed him as protector of the standard and as understudy annalist.
In fact, Sleepy was a young woman, who had been badly abused at the hands of her own family. She fled willingly into the embrace of the Black Company to avoid continued assaults, not bothering to disclose her true sex. When Murgen and Croaker discovered the truth of Sleepy's sex during a medical examination, they also chose to keep silent on the matter, though Sleepy's identity eventually became known when she became a prominent lead in the Black Company's ranks after the Captured were interred beneath the Plain of Glittering Stone. Sleepy was now the Captain, and Sahra (though not officially a member of the Black Company) took on many of the tasks of Lieutenant. Sleepy and Sahra kept the Company alive during the disastrous Kiaulune wars, during which they were repeatedly defeated by the Great General, Mogaba.
During the period of the Protectorate, Sleepy served as Annalist and tactician of the Company while leaving many matters of administration to Sahra as they sought their mutual goal of releasing the Captured from beneath the plain. They resisted Soulcatcher and her regime both passively and actively, gathering information, spreading rumors, creating disturbing graffiti messages, all by-blows to keep the Protectorate distracted while they searched for a way back onto the plain to release the Captured.
Eventually, Sleepy was able to force the truth of the Nyueng Bao's past – or, at least, a version of it – from Uncle Doj. Learning that the Nyueng Bao had possessed another working key to the shadowgate and with the benefit of Willow Swan's first-hand knowledge of the plain and Murgen's ability to leave his own body, Sleepy launched her master plan, evacuating the city of Taglios with virtually the entire strength of the Black Company. She sent the Company south in bits and pieces, and in disguise, while she and Doj recovered the Nyueng Bao's key, a golden hammer that doubled as one of the most significant relics of the Deceivers. Using the key, Sleepy led the Black Company to the Fortress With No Name and ultimately was successful in rescuing the Captured.
Even with Croaker and Lady restored to life, Sleepy found herself thrust into a leadership position, as Croaker abdicated his office of Captain in favor of his former post as Annalist, and Sleepy as elected as Captain of the Black Company. She rallied the Company in Hsien where, over a period of several years, the Company grew from a few hundred raggedy hired killers into a professional army of well-trained and well-equipped soldiers numbering over ten thousand.
Sleepy led the renewed strength of the Black Company back to the homeworld to secure once and for all the Company's retribution against Soulcatcher and Mogaba. The Company won a series of victories advancing north, including a hard-fought victory against the Middle Army with the support of Soulcatcher herself, a battle won mostly because Soulcatcher was incapacitated by the Khadisa, left in a gradually worsening comatose state, and replaced by the Daughter of Night. Sleepy continued to advance her army after the capture of the incapacitated Soulcatcher, with only Mogaba left to avenge herself upon.
During the Battle of Taglios, Sleepy was caught with a small party of her command staff in a mechanical trap under the Southern Gate. She and her companions were trapped by falling stones, and then slain by boiling oil, without any chance of escape. Her lieutenant, Suvrin, replaced her as Captain of the Black Company.