Ephira was once one of the many Hamadryads in Fablehaven, and was said to be flirtatious and bubbly. She fell in love with Marshal Burgess, Patton Burgess's uncle, who was the caretaker then. The love was mutual, so she renounced the trees and married him. Their coutship was said to be brief and passionate She quickly became Patton's favorite relative. Patton once said that it was through her guidance that he became fairystruck. Unfortunately, the relationship between Ephira and Marshal was short-lived. It unraveled within months. Ephira was crushed. She had given up immortality to be with him, and he betrayed her. The anguish and betrayal poisoned her reason Ephira abandoned Marshal and disappeared, in turn, becoming obsessed with gaining her status as a hamadryad.She visited many for help, including Muriel and the swamp hag, who directed her to Kurisock the demon. Kuristock told her to cut down her tree with her own hands, burn it, and bring the last seed to him. Ephira obeyed him. Despite that her connection to her tree was broken, it was mendable, like all broken magic. Kuristock bound himself to the seed, but Ephira did not turn into a Hamadryad. She became something else. She was dark and spectral, tainted by demonic power, a negative of her former self. Merging with Kuristock only magnified her vengeful feelings She then returned to the manor, destroying Marshall and the others that lived there. Patton only barely got away, managing to take the key pages to the treaty from the register before he fled since then, she has always inhabited the Manor, only leaving on Festival Nights.
Ephira is seen twice in the first book. Once, she is outside Kendra and Seth's attic window on Midsummer's Eve. When Seth opens the window, thinking to save a baby that is a monster in disguise, he lets in several monstrosities. Fighting her way to the window, Kendra slams it shut, preventing Ephira from entering the house.
Later, Ephira is seen battling along side Muriel after she has released Bahumat. She stays for a small time, but leaves when Kendra turns the tide of battle with the Fairy Army.
After Seth escaped from Olloch the Glutton, he found the Old Manor, which Ephira inhabited. She appeared as a dirtdevil, or wind storm, but Seth wasn't fooled. When the Sphinx allowed Navarog to escape, Navarog took the Revenant's nail and gave it to Ephira and Kurisock. Ephira put the nail in the tree, increasing her and Kurisock's power.
With Kurisock and the nail, Ephira began the Shadow Plague, which infected most of Fablehaven's inhabitants, turning them into dark, evil, twisted versions of themselves. While the mythic creatures infected joined her side, the humans infected remained self-possessed. Those creatures and people not infected were forced to flee to the naiad's pond with the Fairy Queen's island shrine, which was protected from any being infected by the Shadow Plague. Once the Sorensons were there, Seth hinted that whichever being lived in the old mansion might be the source of the Plague, and Lena, who was once again a naiad in the pond, told them that Patton had hidden the Chronometer in the same mansion. The Sorensons led a raid on the manor to steal the Chronometer. They succeed, but Grandpa and Grandma Sorenson, Dale, and Warren are all captured and turned by Ephira. Seth enters the manor, finds the Chronometer, and brings Patton Burgess, Lena's deceased mortal husband, forward in time several decades. Seth and Patton return to the pond with Hugo and the Chronometer, where Patton goes on to once again woo Lena from the water. Following this, Patton ferries Kendra across the pond to the island in a gut wrenching boat ride threatened by naiadic assaults. They succeed, and Kendra goes to the shrine to commune with the Fairy Queen for the second and last time while at Fablehaven. The Fairy Queen explains that she has watched the whole situation through the eyes of her fairies. She decides to destroy her shrine, and uses the energy to create a small pebble, infused with light and magic. She gives it to Kendra, telling her that touching it to the nail will destroy the nail, Kurisock, and Ephira. However, she warns Kendra that whoever connects the two talismans will die instantly. Kendra and Patton return to the boardwalk to rally support for the plan they develop. The two them explain the situation to Lena and Seth, and go on to persuade many of the mythical creatures to help in their planned assault on Ephira's tree and Kurisock's tar pit. The next day, with an army of satyrs, hamadryads, fairies, dryads, and many others, they set out to battle. They meet very little resistance until they cross over in to Kurisock's domain proper. There, they encounter all manner of darkened creatures. Kendra quickly discovers her touch, when complemented by the power of the pebble, is able to overcome and cure the Shadow Plague. As the attackers come in sight of the tar pit, Ephira arrives. She quickly douses the light of many creatures, almost as fast as Kendra can cure them. After a short but costly battle, Lena takes the pebble and connects it to the nail. Kurisock is slain and Ephira is reduced to dust, ending the threat of the Shadow Plague.
She appears as a beautiful woman swathed in writhing garments. She has black hair and a translucent face. Her eyes are empty, and she radiates fear.