Kilowog is one of the main characters of the Green Lantern series. He is a Bolovaxian member of the Green Lantern Corps. He is a drill instructor, responsible for teaching and mentoring newly-recruited Green Lanterns in Oa.
While he served the Corps, Kilowog's planet was destroyed. Wiping out his people and most importantly his family. Kilowog continued to serve the Corps and became close friends with Hal Jordan, the Green Lantern of Earth. He originally trained Jordan as a new recruit when he was first inducted into the Corps.
Kilowog aided Jordan on their escapade in Frontier Space to confront the Red Lantern Corps after the group attempted to murder a Green Lantern, nine months after the murder of M'Ten. Kilowog and Hal were joined, in their quest, by a Red Lantern named Razer, who they originally wanted to keep captive before he saved the two from their certain deaths. Kilowog would argue with the rogue Red Lantern frequently on their quest and continued to do so up until the defeat of Atrocitus.
Kilowog returned to his previous position of training young Green Lanterns before he was recruited by Hal for a new team to face off against Anti-Monitor, a being seeking to destroy the universe and eliminate all of existence.