Micheal Joliet? You don't know where you heard the name before, but you've used what you know of the Sereitei's records to piece together this much into a standard-ish file format, though some of the data is corrupted junk.

Name: Micheal Joliet
Age: 200?
Rank: Captain of the Royal Guard
High Commander of Royal Human Affairs Division
Previous ranks: Captain of Fifth Division
Commander of Onmitsukido Human Affairs Division
7th Seat of 2nd Division
Height: 6'1 3/16" / 186cm
Weight: 170 lb / 77kg
Eyes: Black
Hair: Black, looks akin to spines or quills
Non-uniform accessories: Sunglasses

Zanpakuto
Sealed form: French-style b*****d sword, 90cm blade, simple and unadorned.

Shikai:
First Phase: Adonai
Sword form: Scottish-style claymore, 105cm blade, ruby-studded hilt
Ability: Allows Micheal to detect and alter inorganic chemical substances around him.

Second Phase: [Corrupted data]

Third Phase: [Corrupted data]

Bankai: [You weren't even able to find any records on this. Micheal is listed as having one in the Captains' rolls, but there's no record at all of him even having trained for it under anyone.]

Known kido:
As former Captain of 5th Division Micheal is known to know all numbered kido and have access to unnumbered or forbidden spells as well. He may have also invented spells that are as yet unknown.

History - Shinigami:
Micheal graduated from the Shinigami Academy in the class of 1831 as valedictorian, enrolling in the Onmitsukido Basic Training and graduating from that in 1836. In 1849 he spoke in front of the Central 46 and his request for a Human Affairs Division of the Onmitsukido, headed by him, to deal with the Quincy threat after 150 years of failure by the Gotei 13.

Little data exists on Micheal after this, except for a record of his appointment as Captain "with promotion postponed until 1914". After taking his position as 5th Division Captain he used data from his reports on the Onmitsukido's projects to author papers on shinigami ethics, most notably An Inquiry into the Defense of Humanity in 1921, A Treatise on Immortal Ethics in 1925, The Dangers of the Neglected Class of the Rukongai in 1929, The Power of Human Corruption in 1934 and On Gullibility in 1947. In 1961, he was promoted to the Royal Guard, after which no further records exist.

History - Human:
You've found that you can trace Micheal through the actions of Joliet Corporation, a semiconductor giant. It popped up shortly before Prohibition as a typewriter manufacturer and slowly rose up through the ranks, almost unhindered even by the depression. Joliet entered electronics and decoding in World War II and helped to manufacture Alan Turing's bombe for the decryption of the Enigma code. Since then it has remained mostly under the radar, and it took a lot of digging just to find out that its corporate threads are stretched such that the entire city of Vancouver, Canada is effectively controlled by Micheal. You still have no idea exactly how much further the threads go, though.

Personality analysis: Micheal appears intelligent and quite calculating, almost indifferent to the needs and desires of others. You really have no idea what goes on inside his head, though.

Other notes: Most of the information you've been able to gather suggests that when he returned as 5th Captain, Micheal had gained some new abilities. Notably, he seemed to have an intimidating presence and many individuals you talked to remember feeling strangely willing to bend to his desire, though he was good at verbal manipulation nonetheless; it also seems to be impossible to lie to Micheal.