Su-mil was an Eickarie from the planet Kariek. Shortly before 22 ABY, he joined the military of the Empire of the Hand, and became a stormtrooper with the 501st Legion, using the warrior name Grappler.
Originally, Su-mil was a freedom-fighter with the resistance on his homeworld. He first encountered the four troopers of stormtrooper Unit Aurek-Seven during the battle to liberate Kariek from "the Warlord," and after the battle, squad leader Twister offered him a position in the military of the Empire of the Hand.
Su-mil became a stormtrooper, and after Twister's retirement, replaced him in Aurek-Seven. He seems to have risen rapidly to the position of squad leader, and remained with the squad until at least 22 ABY. In that year, Grappler and the other three troopers of his unit accompanied Chak Fel to the Redoubt, and participated in the Battle of the Redoubt.