The Legion of The Hidden

A cult, believed to have originated from Sersinara. They are typically outfitted with masks of varying designs, more prominent members of the cult appear to wear more elaborate masks.

Appearance in Tale of Two Sisters

The cult first made its appearance in Tale of Two Sisters: Episode 02 - Akionetakoro at the attack on Akōra. It seems they had been overwhelmed with the resistance of The Nenrai and The Crimson Companions and retreated back to Sersinara taking Tillina Kinato.
Animaera Ilntero has made claim that the ones that attacked The Crimson Companions are known as The Legion of The Hidden, headed by a person named Arseira.
The Crimson Companions are believed to have defeated Elluin, the same archer who killed Janaya Ilntero in Festival of Masks (Akōra).
Vesryn who appeared in Tale of Two Sisters: Episode 08 - The Viper & The Beast is believed to also be a member of The Legion of The Hidden and had nearly taken Wilhelm Ironbark's life.