Mnemosyne (ムネモシュネ, Munemoshune; Greek: Mνημοσύνη, Mnemosyne) is the Titaness of Memories and one of the six Titanesses released by Pontos along with the Titans Okeanos and Kreios. She is also the elder sister of Cronus, the king of the Titans.
She has a frail, childish appearance and cloudy eyes, but she does not appear to be blind. She is very calm and quiet.
During the Titanomachy, Mnemosyne was secretly Zeus's consort and became a traitor to the Titans. She helped orchestrate their defeat by stealing Dark Lightning Koios's "Keraunos", the Thunder Bolt, which had the power to destroy gods, and giving it to Zeus, who used it to overthrow Kronos, his father. However, it would appear that she was not spared by Zeus for her aid; she was imprisoned in Tartarus with the rest of her family.
She is revived centuries later by Pontos with her siblings. Due to her power over memory, she is the one the other Titanesses turn to to understand why Kronos lost his memories after being released. Mnemosyne's intervention in battles has been limited, but it is revealed that she plays an important role as Pontos's ally. Only Dimension Iapetos and Ebony Hyperion have realised that she has been manipulating the Titans' memories, including Kronos's, weakening them so Pontos can use them freely to fulfil his plan. However, Menmosyne's motivations and the true extent of her powers are yet unknown.
Skilled warrior, through divine Cosmo has super strength, super speed, enhanced durability, telepathy (sealed Titans could exacerbate from Tartarus humanity's fighting instincts, risking World War III, and she's the most powerful telepath even among unsealed Gods), telekinesis, energy blasts, forcefields, levitation/flight, dimensional travel, higher senses to track people and events over long distances and through dimensions and soul manipulation (even sealed Titan's power from Tartarus could passively resurrect mythological beings and people all over Earth). Through Dunamis has matter and energy manipulation at the atomic level and reality warping. Through Dunamis and Ichor (divine blood) has regeneration (low-godly) and immortality (mix of types 1, 3 and 4). Can heal and empower other beings through her Ichor and Dunamis.
- Memory seal (記憶解除, Kioku Kaijo): Her transcendent (among Gods) power to manipulate, steal, freely alter and shape into tangible form the memories of beings. Through this she could massively restrict the capabilities of the former Olympian threat Titans (even reducing Kronos to a defenseless child with no Cosmos and close to no memories) so that they'd be closer to the level of Gold Saints, created Hyperion's memories of Apophis, the Egyptian God, or giving Zeus the Keraunos that Koios tried to seal inside his own memories. These seals could only be broken through the death of the victim or by Mnemosyne herself (Hyperion couldn't retrieve his memories by himself after learning the truth and Koios had to accept his own death to slowly remember), and they were still in effect while she was sealed by Zeus inside her Soma.
- In Greek Mythology, Mnemosyne is never stated to have betrayed the Titans during the Titanomachy. However, she did become Zeus's consort after the demise of Zeus's first wife, Metis, but this took place after the war with the Titans. She is also the mother of the Nine Muses, born from her union with Zeus. Additionally, in the underworld is a spring of water named after this Titaness, which has the power to restore a person's lost memories if they drink from it.
- Mnemosyne shares the control over memories like her mythological namesake. The term "mnemonic" (a word used to memorize something) is named after her.
- In the original tale of the Titanomachy, Zeus received his thunderbolt not from Mnemosyne, but from her younger brothers, the Cyclopses, whom Zeus freed from Tartarus when the war began.