Knuckles the Echidna is a teenage echidna that guards the Master Emerald. He's one of Sonic's many enemies.
Knuckles is red with slacked down spikes. His chest is adorned with a white swooshed crest symbol. He wears green-yellow-red Nike sneakers, spiked gloves, and has black eyes with white schelra.
Knuckles is cold, calm, and collected, but has a strong sense of pride and gets boastful more than a few times. He's an introvert and remains aloof, the feelings of solitude and sounds of silence relaxing him. He gets insanely protective of stuff such as the Master Emerald for example, and becomes vengeful if they're stolen. He has an irrational hatred for Sonic, which is said to be because he envies his free life, and that's hypocritical since he's happy with his own life. He's also tough and willing to start a fight, as well as extemely nagging and annoying, and values his personal appearance as much as he does his abilities and possessions. This makes him a narcissist.
It's unknown how long Knuckles has been bullying Sonic, but the 5 year difference between the two of them creeps Sonic out. It's commonly known that they met on Angel Island, Knuckles knocked Sonic out of his super form, and Sonic probably introduced himself. Sonic was harangued by Knuckles so much, he became depressed and he thought his life was miserable. However, Sonic cheered up once Knuckles decided to join forces with him just for a while when Dr. Robotnik stole the Master Emerald and zapped him as he tried to get it back. Of course, Knuckles stayed true to his promise, and after they got the Master Emerald back, he went back to hating Sonic.
When Knuckles and Fang teamed up with Dr. Robotnik to steal the Chaos Emeralds, Knuckles was captured and thrown into an energy cage after Sonic defeated him as Robotnik declared he had failed him. He had no choice but to have Sonic rescue him, begrudgingly thanking him when he did while also swearing revenge.
Sometime later, he befriended Shadow and Silver and they all spent their days harassing Sonic. During the Sonic Forces arc, he along with Silver and Shadow agreed to work for Infinite, but they were stopped by the Sonic Forces, who travelled into the alternate universe along with them.
Like everyone else, Knuckles harnesses Chaos Energy.
Knuckles has gratuitous parkour abilties, as being an echidna, he can glide, and stick to walls like glue. He uses this, and his ability to burrow through the ground, as part of his espionage skills.
Knuckles is an expert at karate, espionage, and thievery; he usually ties up victims before he exterminates them.
Knuckles' one true weakness is electricity, as shown when he gets zapped in Hidden Palace Zone.