|“||Despair, Annabeth Chase! I am Mimas, born to slay Hephaestus. I am the breaker of plans, the destroyer of the well-oiled machines. Nothing goes right in my presence. Maps are misread. Devices break. Data is lost. The finest minds turn to mush!||”|
When Piper and Annabeth Chase descended into the Temple of Fear seeking the statue of Ares, they encountered Mimas, who repeatedly attempted to hit them with his sledgehammer. As a plan of action is useless against Mimas, Annabeth and Piper resorted to fighting him on pure emotion. Piper manages to slash the giant across the back of his knee with her sword, causing Mimas to bellow in outrage.
As Piper and Annabeth ran from him through a tunnel, Mimas taunted the girls as they maneuver through the darkness. He nearly struck Annabeth, but Piper saved her in time and retaliated by stabbing him in the knee. The wound instantly healed, and Mimas reminds the girls that it took two gods working together to kill him during the First Giant War. Piper faced him, telling Mimas that the statue of Ares was not to chain the spirit of war in Sparta, but rather to contain the terrible power of the makhai. While Mimas laughs her off, Piper charged at him with her blade, causing the giant to stumble backwards into a wall and destabilize the temple.
In his anger, Mimas insulted Damasen, inciting Annabeth's rage. He barely managed to deflect her attack, and as he reaches out to grab Annabeth, Piper sliced off Mimas' dreadlocks and his ear. Before he could recover, the girls ran through yet another doorway, with Mimas threatening to bring down the temple's entire chamber upon them. They ran back to Mimas, this time behind the oblivious giant, and slashed both legs, bringing him to his knees.
While Annabeth was keeping Mimas occupied, Piper released the makhai from the statue of Ares, much to the giant's outrage. When the makhai seemingly disappear and "abandon" Piper, Mimas charged her with his hammer, but was stabbed by Annabeth in the thigh. As he staggered off-balance, Piper delivered the final blow by stabbing the giant in his gut. Mimas toppled face-first into the nearest doorway and disintegrated into ash when the stone face of Phobos falls onto him, as the god apparently decided to intervene to help get rid of him after Piper sacrificed the cornucopia to get the makhai.
Mimas is a twenty-five foot tall giant (comparatively short), with his skin and dragon-scale legs as black as charcoal. His long oil-black hair is littered with copper wires and smashed circuit boards. He wears coal-black (possibly Stygian iron) armor, and carries a massive sledgehammer in his hands.
- Battle Prowess: Despite being short for a giant, Mimas is shown to be a very powerful warrior, since he was able to fight Hercules along with Hephaestus himself in the First Giant War, and only lost after Ares began fighting Mimas as well. In The Blood of Olympus, Mimas was able to battle Piper and Annabeth, both highly skilled demigods in their own right, at the same time.
- Reality Warping: As the bane of Hephaestus, Mimas claims that nothing goes right in his presence; maps are misread, devices break, data is lost, and "the finest minds turn to mush". Hence, attacking him with a plan of action will never work.
- Giant Invincibility: As a giant, Mimas can only be killed by a god and demigod working together, and when he is harmed by anybody else, he heals at an accelerated rate. He was originally killed the first time around through the combined efforts of Hercules, Ares, and Hephaestus, and the second time around in The Blood of Olympus through the combined efforts of Annabeth, Piper, Phobos, and Deimos.
- In the glossary of The Blood of Olympus, Mimas is erroneously referred to as the bane of Ares, rather than Hephaestus. However, as mentioned by Mimas himself, he had to fight Ares when Damasen refused to take part in the First Giant War.
- Mimas has a particularly intense hatred for his brother Damasen, since the latter's unwillingness to fight Ares directly contributed to Mimas' own defeat.
- Interestingly, the defeat of Mimas is one of the few instances during which Ares and Hephaestus cooperated with each other very productively.
- Mimas is also a moon surrounding Saturn (planet) that was discovered in 1789 and is named after him.