Responsible for the initial creative spark is Erasmus Brosdau, who is working at Crytek, Germany, as Senior Cinematic Artist. He brings a lot of experience to the project, having worked on 3D since he was 19, and having gotten his first 3D-modelling job at 22. The man's put out a few rendered fan-images for 40k over the years, but decided his next big hobby project would be a feature film of about 10-15 minute length - and he initially worked on it on his own.
By now, the project has evolved from his early ideas, posted in April 2010 (even then he expected the project to take up 2 years time, and around 20.000 frames - which would've taken around 100 days to render on 9 QuadCores(!)), and so has the team and project scope.
Rather than facing the threats of the Immaterium on his own, the team working on The Lord Inquisitor spans around 15 people, with more volunteers chipping in. The team includes industry veterans, professional composers, artists and writers.
In fact, the writing was given over to Aaron Dembski-Bowden, an author for Games Workshop's own Black Library publishing arm, who also happens to be a fan-favorite by now.
The project can also pride itself on having gotten official permission from Games Workshop to proceed and use the IP. People familiar with anything GW will know that their lawyers are absolute bloodhounds, ready to sue violations of their property rights on a brink, and even when the case is not at all clear-cut. For Erasmus and the Lord Inquisitor to have gotten official permission is, in itself, a huge achievement already.
Marcus Allenbrisk is a character created specifically for this project, whereas Torquemada and the Grey Knights are from the background material.
The Grey Knights are a Chapter of the Space Marines that stands aside from the rest of their kin - their gene-seed is modified and said to feature aspects of the Emperor's own genetic material. Their recruitment of the Grey Knights, the Chapter designated as 666, is especially testing - aspirants are chosen based on psychic abilities, will be mind-wiped, given new names and go through extreme trials before making it to the ranks of the Grey Knights - if they survive.
The Chapter has its roots in the Horus Heresy, 10,000 years prior to the present 41st Millenium. Where their creation was shrouded in mystery, their existence is still held as a secret, only known to the Inquisition and select Space Marine Chapter Masters. They are following the requests of the Ordo Malleus of the Inquisition, also known as the Daemon Hunters.
And that is exactly what the Grey Knights excell at. Their psychic powers, and psy-bound weaponry, are devastating to daemonic enemies. They use telepathic links among each other to coordinate their actions, but are masterful warriors each and every one. Their losses, however, hurt the Imperium of Man dearly, as the creation of more Grey Knights is, as already mentioned, diffuclt at best.
Author Aaron Dembski-Bowden released a Grey Knights novel back in 2012, called "The Emperor's Gift". The novel dealt with questionable assignments, finding your place in the psychic network between brothers, and loss. It also dealt with the 1st War for Armageddon, pitching the protagonists against Daemon Primarch Angron and a myriad of Greater Daemons.
Having read the novel, I can assure you that AD-B certainly knows how to write the Grey Knights in style, and that his narrations are well-suited for animated presentation. Even if you are not a 40k fan, or not even familiar with the setting, you'll still find enjoyment from it on the merits of being an action-packed story.
Another trailer is due to be released soon, and in anticipation of that, here is the old Winter 2011 trailer.
This trailer was released when the project was still down to Erasmus alone - the quality in animation and modelling has increased significantly since. Check the Website to stay up to date!