The Inquisitor is the leader of the Inquisitorius He never had a name his whole life. He was a disgrace to his family due to his emo behaviour and got kicked out of the family and had to find a job to save his unemployed ass. Palpatine would have Jerec train him to do jobs that should have been done by Jerec but Palpatine feared Jerec would be declared non-canon if he left his sight. Jerec once said "Palpatine if you are going to use somebody other than me we need someone with more powah than this prick."
The Inquisitor was a terrible student who almost never listened to Jerec's teachings, which is why when he grew up and joined the Imperial Security Bureau (ISB) he often failed his missions. He was once put under the direct control of Lord Vader (Don't ask how that happened) he was sent to dispatch a band of Jedi insurgents on Lothal , the Inquisitor was soundly beat by a half trained Padawan and a Youngling no less. He called Lord Vader for assistance but Vader was extremely angered that the Inquisitor had been beaten by a child, so Lord Vader unloaded a can of whoop ass on the Inquisitor.
Relieved From DutyEdit
Due to the Inquisitors constant failure Lord Vader sent The Inquisitors Teacher Jerec to relieve him from his duties as Inquisitor for the Empire . Jerec used the Force to choke the Inquisitor and to break his body, when Jerec was through with the Inquisitor he lay defeated half dead on the floor in a crumpled mess...
This Inquisitor guy lived on for a several years regaining some of his former strength, he was trying to track down Anakin Skywalkers former master in an atempt to kill him and regain his position as an Inquisitor. He tracked Obi Wan to Tatooine were he confronted Ben Kenobi but due to his horrible fighting skills and his ridicules Lightsaber he decapitated himself and died before his body hit the ground, Ben stood over the Inquisitors body and silentely laughed to himeself he muttered "what a stupid Alien"
Disney Canon. Edit
In Disney canon, the Grand Inqusitor was a male pau,an from the pond planet with screaming lizards. He was trained by Darth Vader in the dark side and probally insulted Vaders suit at some point. He was sent to the planet Lothal to kill the Jedi survivor Kanan Jarrus and his new padawan Ezra Bridger
The inqusitor easily beat both jedi in their first enco useing his buzzare double b spinning Lightsaber. He battled the pair many more times while hunting them until Kanan was captured. When Ezra rescued him on Tarkins star destroyer above Mustafar, the Inqustior duelled them one last time. He defeated Ezra but kanan Cut his silly saber in half, the halves starting a chain reaction of explosions below them. The grand inquisitor then let go of the platform he was holding onto , killing him self in the flames below.( it's always some ledge or platform)