Gadsen is a non-canon character that appears in Mortal Kombat: Legacy.
When Raiden arrived at the mental institute, he was assisted by Gadsen for months. Gadsen recorded every session and classified Raiden as a very disturbed person, so he kept him drugged with high doses of ketamine. In their therapy sessions, Gadsen frequently mocked Raiden for his supposed delusions and finally decided to perform a lobotomy on him. Raiden could not stand it any longer and desperately needed to make an escape, so he devised a plan to make an escape with the help of Blue. He attacked several guards but when their tasers only served to strengthen him, Gadsen used a tranq gun to knock him out.
Gadsen then performed a second lobotomy on Raiden and soon after witnessed Blue stab him, causing the god to explode and vanish, much to Gadsen's shock.