Dilgear is half-wolf and half-troll beastman once employed by Rezo the Red Priest.
Dilgear was a mercenary hired to find and take back the Orehalcon statue from Lina Inverse, an item that possessed a powerful relic that Rezo the Red Priest needed to fulfill his scheme. He was hired along side 2 others: Rodamus and Zolf, the Mercenary knight and Sorcerer, respectively. In the series, he is a decent Swordsman, capable of holding his own in battle with even Zelgadis Graywords, with whom he worked for. He can be annoying as an adversary due to his ability to regenerate and tends to be very emotional outside of confrontation. It is noted that he holds a certain level of leadership over the ranks of Rezo's mooks, and is known to be fiercely loyal. He looks down on magic users, stating that their abilities are nothing more than "Cheap tricks" and uses this statement to taunt Zelgadis into battle.
After his final confrontation with Lina and company in the first season of the anime, he, in fact, did regenerate and ended up wandering into Zephilia, Lina's homeland and also home to her big sister Luna Inverse, the legendary Knight of Cepheid. According to Hajime Kanzaka, Luna likes to wander into the woods and feed stray animals and found Dilgear close to death. He apparently passed out only to wake, much to his horror, chained to a giant doghouse in Luna's backyard. She brought him food and immediately started calling him 'Spot'. He would reply "No, Boss! My name is Dilgear!". Luna continued to taunt him with fresh meat until he eventually submitted.
As a mercenary with a sense of honor, Luna eventually grew on him and he now believes he owes her his life and, apparently, the two have become nigh inseparable.
Dilgear makes his debut in the novel and in the first season of the anime. He also makes an appearance in the Super explosive dragon story manga. As for what he's up to now, it's not certain. It was speculated that, in the novel, he died but Hajime Kanzaka came out in an interview years ago stating that he was adopted by Luna.
It is noted that Lina went home to Zephilia exactly once, supposedly after the incident with Rezo the Red Priest either the first or second time in the first season of the anime, saw Dilgear and made fun of him. It is not known how she was received by her elder sister and there is no evidence suggesting that Lina ever went back to Zephilia after this one time.
He is featured in an eye-catch at the end of Slayers: Next with Luna Inverse whom the fandom mistook for Greater Beast Zelas Mettallium. It was later confirmed that it was, in fact, Dilgear.