This Dark Faerie was called to become the elemental guardian of darkness when the Founder created Petaria. Eventually, she plotted against the other guardians, sending creatures to imprison them. She meanwhile took the form of an Erisim and became the Advisor to the Empress of Miamecca, ensuring she didn't take any counsel that could endanger her plans. When the Werhond arrived, they teamed up, but she betrayed him as soon as they located the Wand of Wishing. Fluffy managed to defeat her in the Erisim form before she could claim the wand. Later, after Fluffy had freed the elemental guardians, she confronted the hero at the remains of the Founder's Temple. There, the Werhond revealed that she too would be replaced by a new guardian, so she switched sides and helped Fluffy defeat him.
I've made a errible mistake. For the sake of our world, you must help me!
The Werhond is almost done gathering power, but he needs Guardians to help him absorb the wand's power.
You must destroy the Werhond's replacement Guardians so the REAL Guardians can destroy his defences!
Although I cannot fight with you, I can heal you if you return.
Good fortune to you. I will join the others when all is ready.
During the final fight, she says the word 'Noctor'. It is unclear if this is her name, or just part of a spell. As an Erisim, she looked like this: