Unseen eyes, concealed amidst the towering trees that fringed the shores of Lake Maridalsvanne, watched over the battle as it unfolded. One observer utilised the supernatural perception of a Heroic Spirit, while the other employed freely wielded clairvoyance. These two Servants were contracted to the second Master, Joanne Merethul.
"Hihihihihi! Look at this, Assassin," a voice cackled.
"You don’t have to tell me," Assassin replied, a white death mask obscuring her face. Her long, braided hair wrapped around her body, and her skin was as smooth as shadows. Numerous blades adorned her person.

Fate/Lost Einherjar, Chapter 3