Grimgrim was a Wookiee warrior and, during the Galactic Civil War, a member of a Rebel Alliance unit known as the Rebel Four. The Wookiee carried a blaster but was nonetheless capable of using brute strength to best the forces of the Galactic Empire. During the war, Grimgrim participated in an assault on a secret Imperial base on the planet Vatleria. Although the Wookiee and the rest of the unit overcame the stormtroopers who guarded the outpost, the Rebel Four were plunged into subterranean traps by Darth Vader, an Imperial-allied Sith Lord who was hiding within the ruins. Grimgrim was crushed to death by boulders.
The Wookiee warrior Grimgrim joined the Rebel Alliance at some point during the Galactic Civil War, a conflict in which the Rebels attempted to overthrow the Galactic Empire and restore the Old Republic. Grimgrim eventually became a member of an Alliance unit known as the Rebel Four, a quartet in which the Wookiee served alongside F4-MF, Falaem Onn, and Soo Rcharrz.
Grimgrim was crushed to death in Vader's trap.
At some point before 4 ABY, an informant tipped the Rebel Four off to the location of a hidden Imperial base on the planet Vatleria, a world that had been abandoned by its original population. Under the command of the droid F4-MF, Grimgrim and the others sought out the base to stop whatever Imperial machinations were afoot there. The team eventually discovered stone ruins guarded by Imperial stormtroopers. Confident that the fortress was the base they sought, they sneaked past the guards. Upon F4-MF's command, Grimgrim and the others stormed the base and attacked the last group of stormtroopers there. In the ensuing fray, Grimgrim fought with bare hands, while the other Rebels fired on their enemies with blasters.
Unbeknownst to Grimgrim and the Rebel Four, Darth Vader, Dark Lord of the Sith, detected the Rebels' assault with the the Force and watched the goings-on from a viewscreen inside the fortress. When Vader sprung a trap for the intruders, ropes ejected from the ground and snagged Grimgrim and the others. The Wookiee was separated from the rest of the Rebel Four and dropped into a pit. There, a barrage of boulders tumbled down upon the warrior. Although the Rebel attempted to deflect the rocks with brute strength, the barrage proved too much, and the Wookiee died. Similar traps killed the rest of the unit.
Grimgrim appeared in "The Rebel Four," a comic story that appeared in Star Wars Tales 9. The story was written and illustrated by Jay Stephens, published by Dark Horse Comics, and released on October 10, 2001.