- The giants to the gods:
- Porphyrion is this to Zeus/Jupiter.
- Polybotes to Poseidon/Neptune.
- Alcyoneus to Hades/Pluto.
- Enceladus to Athena/Minerva.
- Otis and Ephialtes to Dionysus/Bacchus.
- Clytius to Hecate/Trivia.
- Orion to Artemis/Diana.
- Subverted with Damasen, who is the good counterpart to the war god Ares/Mars.
- Also, Alcyoneus' lair to Camp Jupiter.
- Jason, Piper, and Leo each have an evil counterpart to themselves in "The Lost Hero":
- Jason has Lityerses, a handsome and skilled swordsman who uses a golden sword and has scars on his body like Jason does, but he is arrogant and intentionally flaunts his attractiveness, unlike Jason. In even further opposition to Jason, who cares deeply for his sister Thalia, Lityerses cares very little for his sister, who was turned to gold by their father King Midas. Both Jason and Lityerses like Piper, as well.
- Piper has Medea, another attractive individual who can charmspeak like Piper, but uses it for her own gain, unlike Piper. She also has connections to the Giants, like Piper does. Unlike Piper, Medea is confident in herself and her abilities. Both women have had a relationship with a hero named Jason, although Piper's was not real but Mist-induced (although it does eventually happen). To make it even worse, Medea manipulated Piper's father Tristan McLean's assistant Jane into tricking Tristan and allowing him to be kidnapped by Enceladus, who tried using him to blackmail Piper into betraying Jason and Leo.
- Leo has two:
- The first is the Cyclops Ma Gasket, who is immune to fire and a skilled mechanic like Leo is, but uses her skills against the Olympians. In opposition to Leo, Ma Gasket is the eldest member of her family who didn't leave her sons Sump and Torque to fend for themselves as Cyclopes should, while Leo is one of the younger members of his family who was thrown out into the streets by his family after his mother's death.
- The second is Khione, the goddess of snow. While Leo can control fire, Khione controls ice. They both have similar parentage as they are both a child of a god: Leo is the son of Hephaestus, while Khione is the daughter of Boreas.
- Octavian is this to:
- Rachel Elizabeth Dare - He serves the same oracular purpose as she does, but he's creepy and manipulative while she's straightforward and nice. They meet in the fourth book; it doesn't go over very well.
- Will Solace - both are descended from Apollo, but while Will who is more of a medic than a seer wants to help make peace, Octavian wants to destroy the Greeks. Will explains that what Octavian was doing was not what Apollo would want in the final book.
Evil Counterpart / The Heroes of Olympus