Mortis Fel was the son of Roan Fel and the executor of the Fel Reforms, which secretly reformed the Military of the Fel Empire-in-Exile. The reforms, described below, formed the infrastructure of the Great Galactic Empire, founded on Coruscant under Malphas Fel in 171 ABY.
After the defeat of the Empire at the Battle of Anaxes in 138 ABY, which brought about overall defeat in the Second Imperial Civil War, the Empire agreed to sign the humiliating Treaty of Bastion. One of the terms of the treaty was that the Empire should disarm to a very low level. The level stipulated for the maximum number of foot soldiers the Empire was allowed was ten percent of the number they had had at the end of the war.
However, with the failure of the Naboo Disarmament Conference in 154 ABY, one year after the Empire had begun secret rearmament, the Empire began to openly, despite it being illegal, rearm. While the Moff Council endorsed and funded research into better equipment, Mortis Fel revolutionized the military itself.
Firstly, he reintroduced the humanocentrist policy concerning membership, believing that it had been speciesism and a break down of communications due to language barriers that had led to the Empire's defeat in the war. However, Near-Humans were allowed to join provided that they held an advanced knowledge of human culture and Galactic Basic Standard.
Secondly, Fel developed new armor for the stormtroopers. He destroyed the old variants that had been used since the days of Palpatine and introduced armor that was much lighter, better at protecting the wearer and was intimidating at the same time. The armor also used a visorless helm so that soldiers could see each other's faces during battle. The idea behind this development was that soldiers would recognize if their friends were under fire and would fight harder to help them.
Finally, the ranks of the Imperial Knights were expanded and a much greater emphasis was placed upon them in battle plans. The Knights would now play a significant role in battle, like the Jedi during the days of the Old Republic.