|“||Sorry about that. I was not myself. But you have reminded me of the sun and the rain and the streams in the meadows. Percy and Jason, thanks to you, I remembered the sea and the sky. I am cleansed. But mostly, thanks to Piper. She shared something even better than clear running water. You have a good nature, Piper. And I’m a nature spirit. I know what I’m talking about.||”|
–Hagno, in The Mark of Athena.
Hagno was one of Nine Nymphs that helped bring up Zeus after his birth by Rhea, in order to hide him from his brutal father Kronos. They had the extremely loud Kouretes drown out the noise of his cries so his father would not hear, and care for him while he grew up. After Zeus came of age, freed his siblings from the inside of Kronos' stomach, and defeated the Titans in the First Olympian War, he awarded Hagno the highest of honors.
In the Series
Later, the gods and the flame of Western Civilization moved on to Rome. A son of Jupiter (the Roman form of Zeus) invited the nymphs to live in a nymphaeum he had built under his house in Rome. He promised that Rome would never fall, hence the nymphs would have a comfortable time there. Hagno and the other nymphs agreed to this and left their home on Mount Lycaeus. Thus, they ended up binding their life force to Rome.
However, when Rome was conquered, the aqueducts were diverted, and the home of the nymphs' master was destroyed. Hagno and the other nymphs couldn't leave because their life sources where bound to the place and their master hadn't voluntarily released them. For centuries, the nymphs were trapped in their once lovely home. The lake degraded, and in the process, the nymphs also degenerated.
Over time, Hagno and the other nymphs were reduced to hideous savages. They even allied with Ephialtes and Otis, who promised them they wouldn't suffer after they've killed Percy Jackson, Jason Grace, and Piper McLean. The three demigods entered the nymphaeum while searching for Nico di Angelo and were trapped by the nymphs. The nymphs dissolved into black oily water and tried to extract the power of rain from Jason, an endless supply of water from Percy, and beauty from Piper by sucking it out of them.
Using the power of the cornucopia, Piper sacrificed the demigods' power and their strength as if they were already dead. Their gifts emerged from the cornucopia in the form of clean water, managing to cleanse the nymphs. Returning to their beautiful selves, the nymphs left to find new homes. Hagno, then told the heroes to follow the diverted aqueduct pipe line to the hypogeum of the Colosseum, where the Alodai twins resided. She then stated that she couldn't wait to see Pan again. Percy was about to inform her that the wild god had faded, but he couldn't bring himself to. With that, Hagno vanished.
She is described in The Mark of Athena as a withered old woman that was so dried up and brittle like a mummy. Her eyes were dark purple, as if the clear blue water of her life source had condensed and thickened inside her. Her fine silk dress was tattered and faded and her hair was once piled in curls arranged with jewels in the style of a Roman noblewoman, but now her locks were disheveled and dried up like straw.
After she is cleansed along with the others, she is described as a young, beautiful nymph with a shimmering blue gown, glossy black curls pinned up with silver and gold brooches. Her eyes were now gentle shades of blue and green.
- Piper remarks how cruel it was that a nymph as ugly as Hagno (before her cleansing) would have the word hag in her name.
- Both Hagno and Amaltheia cared for Zeus. They also both came across a Grace once (Jason and Thalia respectively).