You may think you're a king, but you're going to die like a dog!
~ Maugrim's last words.
Maugrim is the secondary antagonist of The Chronicles of Narnia: the Lion, the Witch and the Wardrobe. He was The White Witch's evil henchman and leader of her wolf secret police, who enforced her law. He was a large male wolf and a capable fighter. He was also the rival of Peter Pevensie.
He was portrayed by Martin Stone (who also played the Werewolf) in the BBC series while in the Disney film, he was voiced by Michael Madsen.
Maugrim was born during the Age of Winter, and at some point joined her Secret Police. It's possible that all wolves were required to join, as wolves legs are known to be moderately longer than those of other canids, which enables them to move swiftly, allowing them to overcome deep snow, making them the ideal candidates for her forces. Over time he rose to the position of police captain, which was no doubt because of his contempt for his fellow Narnians and his fierce loyalty to the Witch. Under his leadership, he and his police force were feared throughout all of Narnia.
Maugrim first led the raid of Tumnus' Cave where the Faun Tumnus was captured and his home left in tatters. Here, Maugrim left a letter to warn and intimidate others passing by, making an example of Tumnus. Maugrim encountered the human boy Edmund Pevensie while guarding the White Witch's Castle courtyard after Edmund mistook him to be a stone wolf. He escorted Edmund into the Witch's throneroom, and after the Witch learned from Edmund his siblings were at the Beavers' Dam, she ordered Maugrim to find them and arrest them. Howling to call his wolves, Maugrim led them all to the dam. Once they arrived, he ordered his wolves to "[t]ake them." The wolves broke inside, finding the dam empty but also a secret tunnel. When they emerged from the tunnel's exit, they found a fox whom Maugrim demanded to tell him where the Human Fugitives had gone, threatening that "[his] reward [was his] life. It's not much, but still . . ." The Fox told Maugrim the Humans headed north, and so he ordered his wolves to smell them out before they took off, sparing the Fox.
Eventually, Maugrim and his wolves caught up with the other Pevensie children and the Beavers at a frozen river. One of his wolves restrained Mr. Beaver while Maugrim threatened Peter to put down his sword, mocking him that someone could get hurt, and chuckling when Susan said Peter should listen, smugly stating, "Smart girl." Maugrim falsely promised that if the Pevensies left Narnia, their brother would leave with them, mocking Peter further that it was not the children's war, lying that the White Witch only wanted Peter to take his family and leave Narnia. He threatened he would not wait forever, nor would the river. Unfortunately, the river did indeed not wait as it burst (due to spring starting to return to Narnia), washing the Pevensies and Beavers away. Angered, Maugrim and his wolves tracked down the Fox and delivered him to the Witch, declaring him a traitor, rallying the enemy in the Shuddering Woods. The Witch turned the Fox into stone and commanded the Wolves to gather the faithful, saying that if it was a war Aslan wanted, it was a war he would get, demonstrating this by casually turning an innocent butterfly to stone, as well.
Maugrim later spied on Aslan's Camp until being exposed by Susan with the sound of her horn. Peter arrived, drawing his sword and meeting Maugrim in a standoff while Susan and Lucy fled into a tree. At first, Maugrim mocked Peter, stating they'd been through this before. They both knew Peter did not have it in him to kill. Aslan arrived, subduing Maugrim's follower, but did not interfere with Peter's battle and urged his own followers not to interfere, either. Maugrim growled to Peter, "You may think you're a king, but you're going to die . . . like a dog!" The Captain of the Secret Police then lunged at Peter, accidentally impaling himself on his sword, killing him instantly. His fate in the book is similar, although there are a few differences. Namely, Maugrim taunts Peter after the latter draws his sword inches away from the former's face. Maugrim then pounces on him, only to be impaled on the sword, letting out a yelp as he dies.
Minutes after Maugrim's death, Aslan had Peter clean his sword and kneel before him before knighting him as Sir Peter Wolfsbane in honor of the evil wolf's defeat.