Calcelmo's Stone is an artifact bearing inscriptions in both the Dwemer and Falmer alphabets.
Cascadia is an enchanted sapphire ring of either Maormeri or Nordic origins. Some sources believe that the ring was crafted by the Sea Elves, but others claim that it was a failed attempt of a Nord enchanter to create a water-breathing ring. Although it does not provide the ability to breathe underwater, the sounds of the ocean can be heard from its stone. It also provides a boon to the absorptive abilities of the wearer, improves their willpower by granting them a defensive boon while casting spells, and enhances their melee combat capabilities.
Around 4E 180, it came into possession of the Warrior.
Chillrend is an artifact of unknown origins. It takes the form of a glass shortsword, although, unlike regular malachite, it is blue instead of green. Like other glass weapons, its hilt was fashioned from rare metals and moonstone. Its enchantment varies in strength and properties, but it always causes magical frost damage to the opponent. Other known effects include causing a weakness to frost, or temporary paralysis. It also repairs itself when the wielder takes frost damage.
Chrysamere, also known as the Paladin's Blade, the Blade of Blades, and the Sword of Heroes, is an ancient adamantium claymore artifact with offensive capabilities only surpassed by its defenses. It has magical properties which, unlike most weapons, are defensive in nature; it lends the wielder health, boosts their resistance to fire, and reflects some damage from spells. It is unaligned, and is not a Daedric artifact.
Cleaver of St. Felms
The Cleaver of St. Felms the Bold (or St. Felms' Cleaver) is a one-handed axe which belonged to the eponymous saint of the Dunmer.
The Coral Heart is an ancient and powerful artifact associated with the Land Coral along the Inner Sea. The heart's connection to the coral is believed to be symbiotic in nature, and it grants the coral the ability to think and reason. The heart appears as a glowing mass with a barely visible piece of metal buried between layers of coral.
Crosier of St. Llothis
The Crosier of St. Llothis is a staff sacred to the Dunmer as a holy relic. The undefeated spirit of St. Llothis the Pious is said to be contained within it. However, the staff's fitness for combat is questionable, as the staff's enchantments actually have various adverse effects on the wielder.
Crown of Barenziah
The Crown of Barenziah is the coronation crown of the eponymous Queen of Morrowind, Barenziah. It is a golden crown with a winged-motif that has twenty-four ornate jewels, known as the Stones of Barenziah, across the wings and one on the temple of the head. It was given to the young queen during her ascension to the throne of Mournhold in the early years of the Third Era, amidst the reign of Emperor Tiber Septim. However, sometime after the ceremony, the crown was stolen by an unknown assailant. He pried each of the stones off of the crown and dispersed them across Skyrim, where they became items of interest. For two eras, the Thieves Guild of Skyrim had sought out all twenty-four stones for many years, while the crown was kept in Morrowind.
Crown of Freydis
The Crown of Freydis, originally the Crown of Verity, was a magical artifact created to test the worthiness of potential rulers of Skyrim. It is the second royal crown of Skyrim, replacing the Jagged Crown when it was lost to time during the War of Succession. However, in time it faded from use, and it has not been seen since the Second Era.
Crown of Nenalata
The Ayleid Crown of Nenalata is an ancient Ayleid artifact. Its appearance varies, sometimes appearing as a lightweight Moonstone helm, sometimes as a simple crown. It can be distinguished from other Ayleid crowns by a royal glyph emblazoned upon it. Superficial enchantments grant the wearer spell reflection and increased skill at Alteration and Conjuration magic, although the true potential of the crown is seemingly much greater. It is an immensely valuable treasure.
The Crusader's Relics are a set of Aedric artifacts, created by the Eight Divines and given to Pelinal Whitestrake, the Divine Crusader. The set includes a suit of armor, a shield, a mace and a longsword, which mold to the needs of the wielder and increase their proficiency in the School of Restoration. The artifacts were used by Whitestrake to banish Umaril the Unfeathered, an Ayleid Sorcerer King. In the battle, Umaril had dealt him a fatal blow, and with his death the relics were scattered and lost.
In 3E 111, Sir Amiel Lannus founded the Knights of the Nine with the intent of recovering the lost relics. The order grew in fame, and recovered many of the holy relics, but after the War of the Red Diamond the knights slowly disbanded, losing all but one of the relics.
In 3E 433, Umaril the Unfeathered returned to the mortal realm, having been reborn in the Fires of Creation due to his alliance with Meridia. The Fallen King led an attack on the Nine Divines by desecrating chapels with his army of Aurorans. Following the calling of a mysterious prophet, a pilgrim set out to retrieve the relics and reform the Knights of the Nine. The pilgrim succeeded, becoming the Divine Crusader reborn and destroying Umaril, body and soul. The relics were subsequently held in the Priory of the Nine.
In 4E 201, the relics and a new set of reforged relics were stolen by a gang of bandits. The Last Dragonborn tracked down the bandits to the ruins at Four Skull Lookout, killed them, and claimed the artifacts.