Erethdor is the elf possessing Solak. He is encountered during the third phase when Merethiel sends the players to Solak's mind.
Erethdor attacks with ranged abilities, has 500,000 lifepoints in group mode and 250,000 lifepoints in duo mode, and players cannot use food to heal themselves while they battle him within Solak's mind. Erethdor will also force players out of Solak's mind after a set period of time. If Erethdor's lifepoints are brought to zero, the next phase automatically begins. Otherwise, all eight green circles summoned by Merethiel around the arena will need to be filled with corruption.
Erethdor was an elite elven warrior sent by Seren to aid Solak, along with Merethiel, Faerdhinen, and Saeldor. Merethiel describes him as distant, rarely showing his true feelings and having an insatiable desire for power and knowledge. They eventually stole a grimoire from the grand library of Prifddinas, which told of a form of magic later known to be blight. Merethiel describes it as extremely destructive, yet calm and yielding. As Erethdor learned more and mastered this magic, he became ever more power hungry, rarely interacting with his siblings and spending virtually all of his time scouring new scrolls. Merethiel later stole the grimoire hoping to learn about what Erethdor was doing, but crucial pages of it had been torn out.
He and his siblings were later tasked by Seren with helping Solak guard the Lost Grove. Here he would eventually learn of the heart of the tree, the grove's most powerful artefact which Solak guarded, and became set on taking its power for himself. He attacked Solak using the powerful blight magic he had learned, but ultimately was defeated by the joint effort of Solak and his siblings, splitting his mind; half of it went to Solak, and the other half in a stone Merethiel would carry with her. He would never forgive his siblings for their "betrayal". Over time, Erethdor's influence began corrupting Solak, prompting the guardian to seal off the Grove to protect Gielinor. He eventually gained complete control over Solak and became a serious threat to the world after the Lost Grove reappeared.
Due to the Lost Grove reappearing, Merethiel recruited the World Guardian and their human allies to stop Erethdor before he could leave the grove. Erethdor fought them using Solak's body and power which he enhanced using blight magic, but the group proved to be stronger than he thought. In a last ditch effort to stop them, he attempted to destroy what little remained of Solak's conscience with multiple manifestations before he could be expelled, but was unable to destroy it in time and his influence was purged from the Guardian. His other half remained in Merethiel's possession, leaving his current fate unknown.
- Erethdor is spelled "Eredthor" when interacting with The Lost Grove ruins.
- Erethdor's life points in duo mode were lowered to 250,000 on 18 June 2018. Previously, he had 500,000 life points in both modes.
- He is the original owner of the Blightbound crossbows, as he wields them in battle and the bows themselves are referred to as belonging to him in the server wide announcement which appears when a bow is received.