|“||Minor goddess? I was old before the Titans were born, you ignorant girl. I was old when Gaea first woke. Misery is eternal. Existence is misery. I was born of the eldest ones - of Chaos and Nyx.||”|
Percy Jackson and Annabeth Chase meet Akhlys so they can hide themselves in the Death Mist to get through Tartarus and close the doors of death. She offers them different types of toxic plants so they could die "peacefully" compared to their uncertain future if they continue their plan, but the demigods rejected her offer and she accepted theirs granting them the death mist. However, Akhlys betrays Percy and Annabeth, using their inability to move with the Death Mist chucking poison at the pair and attacking them with her claws. Percy uses his powers over water to will the poison back to her, which causes her to flee from them. It is during this that a darker force in Percy's personality reveals itself.
Akhlys appears to Nico di Angelo in one of his dreams, saying that he already had so much sorrow inside him that she cannot add to his misery.
Akhlys looks like a victim of famine: She has a drippy nose, sunken eyes, stringy grey hair that is matted to her head, and large amounts of dust covering her thin body. Akhlys also has bloody red clawed cheeks that drip blood on her tattered dress. It is likely that this was actually caused by her scratching herself.
Akhlys appeared on the shield of Hercules as pale, emaciated, and weeping. She had chattering teeth, bloody cheeks, long nails on her fingers, shoulders thickly covered with dust, and swollen knees. Akhlys claims that she is a symbol of the everlasting misery of people.
- Death Mist Control: As the goddess of Misery, Akhlys has control over Death Mist.
- Toxikinesis: As the goddess of poisons, Akhlys has absolute control and divine authority over poison.
- Misery Induction: As the Protogenoi and Goddess of Misery, Alkhlys has divine and absolute control over misery and can inflict anyone she desires with the emotion. Alkhlys can also apparently see and read the memories and thoughts of anyone related misery, As seen where she was able to immediately sense the amount of pain and suffering Nico di Angelo went through and know why he was so miserable.
- Enhanced Agility: Akhlys can run relatively fast when properly motivated. This was shown when Percy rerouted the flow of poison and then began to choke on her own saliva.
- Prowess in Battle: Akhlys shows relatively great prowess in battle, being able to gain an upper hand against both Annabeth and Percy before they redirected her poison back at her. However, it should be noted that the pair's abilities were not as strong due to them not being used to controlling their bodies with the Death Mist.
- Although she is thought to be created before Chaos in, The House of Hades, she reveals she is his daughter. This mirrors how some Greek Creation Myths call Chaos the state before time began and a god, while others proclaim it was Chronos or Akhlys who created Chaos or existed prior to it.
- Some myths list Akhlys as a possible daughter of Nyx among the Keres.