Coldstone is a cyborg gargoyle, created by Xanatos and Demona from the shattered stone remains of three members of the Wyvern Clan who were killed during the Wyvern Massacre, as well as some cybernetic parts. Of the three gargoyles, Coldstone mostly resembles the gargoyle Othello, and Othello's is the dominant personality. Coldstone was so named since he is "cold stone brought to life" and not a flesh-and-blood creature.
The other two gargoyles whose remains were used in the construction of Coldstone were Desdemona (Othello's mate) and Iago (his rival). Their souls were later transferred into robotic bodies, and they are now respectively known as Coldfire and Coldsteel.
Othello was hatched in the year 938, a member of the same rookery generation as Goliath, Demona, Desdemona, Iago and Hyppolyta.  In 971, when he was an adolescent, the leader of the clan whom he called "Mentor" (now known as Hudson) had him on sentry duty and he was the first to approach Robbie and Prince Malcolm when they came seeking the clan's aid, and he escorted them up Wyvern Hill to talk to Hudson. ("Once Upon A Time There Were Three Brothers...")
As he grew older, Othello fell in love with Desdemona, and she with him. They had become mates by 987, when they conceived the egg that would one day hatch into Gabriel. However, in 993 Iago wished to split them apart, since he lusted after Desdemona himself, and so lyingly told Othello that Desdemona and Goliath were lovers.  Othello believed Iago's lie, and fought against Goliath in anger, but Desdemona finally managed to somehow make peace between them. Othello and Desdemona returned to their mated life afterwards in peace, until they were destroyed by Hakon's Vikings, alongside most of the Wyvern Clan, in the Wyvern Massacre of 994. ("Legion", "Awakening: Part One")
In the beginning of 1995, Demona and Xanatos plotted to resurrect another gargoyle to assist in defeating Goliath. The remains of the gargoyle who had been Othello were chosen both because Xanatos had been able to retrieve several pieces of his body (and unwittingly those of two others who had been sleeping nearby) and because Demona felt that Othello's indifferent attitude towards humans was closer to her own than Goliath's.  Bringing Coldstone to life through a combination of sorcery and science, they also unwittingly resurrected Desdemona and Iago, whose souls were likewise confined in Coldstone because their body fragments were part of it, although they did not immediately reveal their presence. Othello's soul was the dominant of the three initially because most of the body parts were his, thus rendering him the identity of Coldstone thereafter.
Demona and Xanatos then duped Coldstone into helping them against Goliath, Demona deceiving him into believing that Goliath was the one responsible for his half-machine condition that had so horrified him when he discovered it. Coldstone fought Goliath first at Times Square and then at the George Washington Bridge, but finally came to understand that he had been deceived by Demona, and saved Goliath from drowning in the Hudson River. He also blocked a shot meant for Goliath from Demona's laser cannon and fell into the river himself; Goliath and his clan mistakenly believed him to have drowned or damaged beyond repair. ("Reawakening")
But Coldstone survived, repaired his own damage and emerged from the river some months later, now controlled by a computer program that Xanatos had installed in him when he and Demona had first "revived" him. Under Xanatos's control, Coldstone broke into the Goldencup Bakery Building and downloaded a series of files on secret weapons being designed for the military there; however, these files were protected by a powerful computer virus that began to destroy his memory banks. This triggered the surfacing of Desdemona and Iago's souls inside him, and both they and his original soul as Othello began surfacing at different moments, all controlling him randomly. Goliath and his clan, re-encountering him, soon discovered his new condition, and Goliath had to enter Coldstone's mind through RECAP's virtual reality hook-up to save him. Iago tried to play Goliath and Othello against each other once again, but failed. In the end, the virus did enough damage to erase Xanatos's computer program and temporarily shut Coldstone down; the gargoyles took him back to the clock tower, in the hopes of someday being able to restore him. ("Legion")
Lexington worked hard at this task, but was unable to make any progress. Demona and Macbeth kidnapped Coldstone under the Weird Sisters' instructions, however, mainly as a decoy to hide the thefts of the Grimorum Arcanorum, Eye of Odin, and Phoenix Gate, but also to use briefly against the clan (while Iago was controlling him). For a time, Othello refused to regain control of his body as Coldstone from Iago and save the gargoyles and Elisa from their enemies, preferring to remain with Desdemona's soul in cyberspace, but at last (with a bit of prodding from the Sisters, masquerading as Desdemona) did seize control of his body, ousting Iago. He helped Elisa drive off Demona and Macbeth and free the clan, but then left New York, unwilling to remain in the area as long as Iago could regain control of him at any point and use his body to endanger the gargoyles once more. ("High Noon")Himalayas for a time due to its isolation. There he somehow encountered Master Dawa, a wise monk, who agreed to work with Coldstone in controlling his inner demons, namely the Iago soul inside him. In mid-1996, the Avalon World Tour brought Goliath, Elisa, Angela and Bronx to Tibet and they encountered Coldstone there. While Coldstone was happy to see his brother and excited to learn that his rookery children were alive and well on Avalon, he knew that he could not accompany Goliath and the others to Avalon and beyond as he was still a threat to his clan and his children if Iago gained control of the Coldstone body. Knowing Goliath and the others would not leave without him, Coldstone pretended to come under the control of Iago and fought the Travelers until they were unconscious. He may have then assisted in sending them aboard their skiff to Shambahla. ("Reunion")
Later, after Goliath helped thwart Oberon's attempt to kidnap Alexander, Xanatos decided to repay his debt to Goliath by finding Coldstone, bringing him back to New York, and constructing two additional robotic bodies to house Desdemona and Iago's souls in, Coldfire and Coldsteel respectively. He found Coldstone in the Himalayas using a built-in tracking device and used Steel Clan robots to capture him.  Taking him back to Manhattan, Xanatos and Owen Burnett began attempting to transfer the two souls into the two robots using technology. When mere technology proved unable to transfer the gargoyle souls to these bodies, however, Owen had to step in by, as Puck, making "Soul Transference 101" one of Alex's magic lessons. The three gargoyle souls in Coldstone were temporarily transfered to Broadway (who housed Othello's soul), Angela (who housed Desdemona's soul), and Brooklyn (who housed Iago's soul). For a time, they were tempted to remain in their new gargoyle hosts, but at last Othello realized that he and Desdemona could not deprive Broadway and Angela of their own lives, and so let Alex transfer them back to Coldstone and Coldfire's bodies. Iago had, in the meantime, already housed himself in Coldsteel, and Coldstone and Coldfire, realizing that he had become more dangerous than before in this form, set off in pursuit of him. They plan to eventually join the Manhattan Clan, but only when Coldsteel is no longer a threat. ("Possession")
Eventually, the couple tracked down Coldsteel to London, England just as the latter was battling with Hudson while Steel Clan robots and Coyote 5.0 were engaging Lexington and members of the London Clan in battle. Coldstone and Coldfire announced themselves by interrupting their quarry's attempt to seriously wound the elder gargoyle and then joined the battle. ("Rock & Roll")
They helped Hudson, Lexington, and members of the London Clan fight off Coldsteel and Coyote 5.0, defending the Stone of Destiny. During the day, the fight continued over the Coldstream Bridge. Coldstone destroyed Coyote 5.0 while Coldfire managed to damage Coldsteel but he fell into the river and disappeared. Later that night, Hudson conviced the pair to leave off the search for Coldsteel and return to the Manhattan Clan. ("Rock of Ages")
Coldstone most closely resembles the gargoyle Othello, his original dominant personality. Roughly half of his body has been replaced with robotics. Coldstone's wings, part of the left half of his head, his right eye, his right arm, most of his left leg, the end of his tail and much of his torso are all cybernetic parts, along with smaller pieces throughout his body. Most of Coldstone's robot parts resemble the corresponding parts on Othello, though he is missing the horn and hair on the left side of his head and his wings are smaller and more angular. Coldstone has a couple of features borrowed from the Steel Clan, including a retracting arm cannon. Coldstone's robotics are metallic grey, red, and gold. His remaining body is re-animated stone, not flesh. (Hence Demona's line "You are cold stone brought to life.") This can be hard to tell, since Othello's skin color is very similar to Coldstone's current coloration.
During the time the personalities of Othello, Desdemona, and Iago shared Coldstone, its likely that each personality had access to information acquired by the other personalities when they were in control, as seen in "High Noon". Due to Iago's personality being dormant the entire time Demona spent with Coldstone when he was first activated in "Reawakening", Iago could not know Demona's name himself (given that she did not even have a name when he was alive).  After Demona reactivated Coldstone (and Iago immediately took over), however, his internal point of view showed that he scanned Demona's face which gave the result "RECOG. DEMONA" and Iago immediately knew that she was a fellow enemy of Goliath that he could work with.
By 1996, the Coldstone could read and write in English and 'maybe a little' Latin and ancient Celtic as well. 
- "Reawakening" (First Appearance)
- "Vows" (No Lines)
- "City of Stone" Part One (No Lines)
- "High Noon"
- "Upgrade" (No Lines)
- "Shadows of the Past" (Illusion of Othello)
- "Future Tense" (Mentioned Only)
- "The Rock" (No Lines)
- "Rock & Roll"
- "Rock of Ages"
- "Rock of Ages" (No Lines)
Real World Background
The name "Othello" was never used on screen for the pre-Wyvern Massacre version of Coldstone in the actual series; it was used in the script (because humans and production staff need names), however, for this character to fit the symmetry of Desdemona and Iago's names. The name, of course, derives from the title character of William Shakespeare's famous tragedy, Othello, the Moor of Venice, who similarly is married to the faithful Desdemona, but duped by the scheming Iago into believing that she is unfaithful, engaged in an adulterous affair with Cassio. In anger, Othello smothers his wife, and then, discovering how Iago had duped him and that Desdemona was innocent, commits suicide in remorse.
Voice Actor: Michael Dorn
Coldstone is often said to be the Gargoyles Universe's equivalent of Frankenstein's monster (with Xanatos taking the role of his creator, Dr. Frankenstein). Though Coldstone's story does not directly follow Frankenstein's, there are some major similarities. The creation of Coldstone is an obvious homage to classic depictions of the birth of Frankenstein's monster, right down to Xanatos's self-indulgent "It's alive!" line. Neither Frankenstein's monster nor Coldstone turn out exactly as their creators intended. The episode "Legion" is partly inspired by a TV movie version of Frankenstein Greg Weisman saw as a boy, in which the monster is put under hypnosis and the various personalities of the people whose corpses were used to make the monster being to speak, including one who quotes the Biblical line "I am Legion, for we are many".  In the original novel by Mary Shelley, the monster escapes to the Arctic Circle, with his creator in pursuit. Coldstone, attempting to keep the rest of his clan safe from Iago, ended up in a similarly cold and desolate part of the Himalayas, where one of his creators eventually finds him.
Coldstone's blue-grey skin color is a bit of a mistake, or at least something of a problem. It's pretty much identical to Othello's skin color, but it is intended to be re-animated "stone," not the flesh of a gargoyle awake at night. Because Othello's skin color is nearly the same as Coldstone's, it's very hard to tell that Coldstone is intended to be living stone and not living tissue. This confusion can make Coldstone's design seem like something of a cheat when it's revealed that he was assembled from pieces of three different gargoyles. If you think that the visible non-mechanical parts of Coldstone are skin, you might wonder why he doesn't have any patches of skin that resemble Desdemona or Iago in color.  Artistic license is largely to blame for Coldstone having white hair that should otherwise also be re-animated stone (although Greg Weisman muses that the process involved in Colstone's revival could have had an effect on his hair returning white. That, or it's just "VERY LIGHT GRAY" stone)