Shadow Avalon took his original's place as a professor at Alfea, creating an obelisk and a dark storm as part of a test for the fairies. Tecna suspected him to be the Angel of Doom, but this was proven false.
Sneaking around with a hood, Shadow Avalon cast a homesickness spell on the pixies so that they would lead Darkar to Pixie Village, but this was foiled by Bloom. Later, Shadow Avalon afflicted Bloom with a shadow virus to turn her into Dark Bloom so she would steal Alfea's codex for Darkar, and only turned her back after she gave the codex to Kerborg. He also faked illness after being attacked by a poisonous plant in order to get Livy to go to Pixie Village for an antidote, leading Icy to the codex hidden there.
When the real Avalon escaped from the dungeons of Shadowhaunt, Shadow Avalon's true identity was revealed, but he captured Bloom and took her to Darkar, who turned her into Dark Bloom again. Shadow Avalon is not seen following this and was presumably destroyed when the Winx destroyed Darkar, as Shadowhaunt crumbled with Darkar's demise it is likely all his Shadow Monsters were as well.