Wraith

Wraiths are shadow creatures that appeared in Arden during the time when unicorns started to get hunted. There's a legend that says if you kill a unicorn, you'll be immortal. The Gemmers thought this was true and went on unicorn hunts, leading up to the Unicorn Massacre. Instead, the Gemmers became wraiths, which attacked the rest of Arden, by giving them wraith-burn. Wraiths' only fear is sunlight and unicorns. Claire defeats all the wraiths by awakening the Memorial of the Missing.

History
The Gemmer army became wraiths when they killed unicorns.

Nett's parents were attacked by wraiths and died.

The Unicorn Quest
A wraith attacked Sophie and Claire. Nett made the maribo glow to drive the wraith away.