Knuckles the Echidna from Sonic the Comic is a red anthropomorphic echidna, the last of his kind (at least initially). Completely alone, he guards the Floating Island, as well as the Chaos Emeralds and the Master Emerald, a duty he takes very seriously.
Unlike the games version of the character, he does not have a white crescent birthmark on his chest. Instead, he wears a silver-white circlet or necklace.
When the Death Egg crashed on the island, Knuckles was briefly duped by Doctor Robotnik into believing Sonic was a dangerous villain who plotted to steal the Island's Chaos Emeralds. The echidna thus allowed Robotnik to place his Badnik armies on the island and also construct a Launch Base Zone to rebuild his Death Egg, and assisted him in fighting Sonic and stealing Sonic's own six Chaos Emeralds so they could be combined with Knuckles' into one set of Emeralds (the original state of the Chaos Emeralds). Knuckles, however, didn't trust Robotnik enough to tell him that he had the Grey Emerald (which could control the others), and when Robotnik tried to absorb the Emerald's power into himself, Knuckles used the Grey Emerald to defeat him.
Knuckles spent the next few months destroying every trace of Robotnik's influence on the Floating Island, including the entire Carnival Night Zone, and assisted Sonic both when his secret base came under attack by a Badnik army and when Robotnik established a base in the Ice Cap Zone. Finally, the two heroes teamed up to destroy the Death Egg before it could launch - which they failed to do, and worse Knuckles had failed to stop Robotnik's Metallix from stealing the Master Emerald to power the Death Egg! While Sonic fought to retrieve the Emerald, Knuckles used ancient echidna technology to pilot the Floating Island and open fire on the Death Egg with Chaos Energy blasts, finally downing the craft.
With the Master Emerald returned, Knuckles owed a debt to Sonic and, despite preferring privacy, agreed to hide the entire population of the Emerald Hill Zone in the Mushroom Hill Zone to keep them safe from Robotnik's wrath. Whilst the arrangement was generally stress-free, the villagers swiftly demanded to be returned home when Robotnik was overthrown.
In the story "The Homecoming", Knuckles discovered that a elderly, white-furred echidna named Doctor Zachary had appeared on the Floating Island. He claimed to be the first of the race to return to Mobius and was being pursued by a dangerous robot, but it turned out Zachary was evil and using the robot (in reality an ancient echidna Guardian Robot) as his minion. He had the robot destroy the Master Emerald and absorb its power, leaving the Island to crash while he destroyed Mobius, but Knuckles stopped him (using the robot's head as a brief substitute Emerald) Zachary apparently perished as he fell from the Island, but later returned, with a part-robot body, working for Robotnik. It was hinted that he knew where the echidnas had vanished to, but his story was left unfinished at the end of the comic.
Knuckles retrieved a new Emerald from the echidna's Sacred Emerald Mines, which existed in a haunted graveyard. In doing so, he had to face the spirit of the Kohenyu, a race of Styrakosaurus who were unwittingly hunted to extinction by the echidnas, and take responsibility for their death. He then was roped into helping Captain Plunder and his Sky Pirates launch a heist on an alien galleon, in return for a chest of ancient echidna documents that could help him with the Island's ancient computer systems. Knuckles trekked across Mobius with the chest, fighting the occasional villain as he went, before finally returning to the Island to battle Robotnik and a cyborg Zachary's attempt to turn the Emerald Hill refugees into an organic computer. When Robotnik was overthrown, Knuckles spent his days with Porker Lewis trying to uncover the mysteries of his lost people, occasionally being drawn into battle against such foes as a D.R.A.T.-affiliated heist team and a Chaos-charged Robotnik.
Knuckles left his island to save lives from the environmental collapse of Mobius, when Robotnik tried to drain the planet's life force. Soon after that (in STC's last story), the Floating Island came under attack by the terrifying Chaos creature and Knuckles was forced to stop it absorbing the Chaos Emeralds by scattering them to the four corners of Mobius - dooming the island in the process. He was left distraught and had to be forcibly evacuated from the island, and joined up with the Freedom Fighters to stop Chaos and retrieve the Emeralds.
Knuckles is also one of the few to know of Tails' legendary status in the Nameless Zone, a fact he became aware of when he followed Tails through a portal mistakenly believing the young fox was being kidnapped. The Nameless Zone residents came to the conclusion that Knuckles was actually Sonic, whom Tails had claimed was his sidekick. Far from blowing Tails' cover, Knuckles was delighted to meet people who didn't worship his rival and played along, assisting him in defeating the terrifying Trogg once and for all.
The last STC storyline revealed that the ancient echidnas had been at war with the alien Drakon Empire, who invented the Chaos Emeralds; Knuckles was alive back then and served as the leader of the echidna's army. It is presumed by Sonic that Knuckles was placed in suspended animation for unknown reasons and lost his memory. Nigel Kitching's original plan was to reveal that the outcome of the war was that the Drakons were driven back but the only surviving echidnas were Drakon slaves scattered across the Empire (and that Zachary was one of these echidnas).