Nudillos, known in English as Knuckles, is a red anthropomorphic echidna and one of the main characters in the anime Sonic X. He is the last surviving member of his clan and serves as the official guardian of the Master Emerald, a powerful gem that controls the Chaos Emeralds and keeps Angel Island afloat. In the series, he is introduced as a mysterious and reserved individual who prefers to follow his own path, often keeping to himself. His strong sense of duty as the Master Emerald's protector defines his actions and motivations, and he is fiercely protective of his responsibility. During the first season, Nudillos appears sparingly and frequently acts as a rival to Sonic, though he is not truly an enemy. He is often deceived by Dr. Eggman due to his trusting and somewhat naïve nature, which leads him to clash with Sonic and his friends. Over the course of the story, his role becomes much more active in the second season, where he uses his immense strength and martial arts skills to help Sonic and the others locate the Chaos Emeralds and oppose the Metarex threat. He is notably the only character capable of wielding the Master Emerald to its full potential, a power that becomes essential when the spaceship Blue Typhoon requires extra energy. In terms of personality, Nudillos is tough, stubborn, and hot-headed, but also deeply loyal once he commits to a cause. He is often jealous of Sonic’s carefree and adventurous lifestyle, yet he remains anchored by his duty. His interactions with Rouge the Bat develop into a complex, often antagonistic dynamic that hints at mutual respect and possible affection. Throughout the series, Nudillos demonstrates notable abilities: his powerful arms and sharp knuckles can shatter rocks and even metal, he is a master of various martial arts, he can glide long distances by using the air under his dreadlocks, and he can climb vertical surfaces with ease. He also possesses the spin dash technique and can transform into a more powerful Super form when empowered by the Chaos Emeralds. Despite his strength, his most persistent weakness is his gullibility, which Eggman repeatedly exploits. Nevertheless, Nudillos matures during the story, learning to work collaboratively with his friends and ultimately sacrificing the Master Emerald to power the Sonic Overdrive cannon, thereby ending his long guardianship. This event marks a significant development in his character, as he has to redefine his purpose beyond his original duty.