Dorm head of the Sea of Estray Faction, and their most powerful member in OLYMPUS. She wields anti-spirit sword “Kuuteräs” and is generally regarded as the normal human that the Servants of OLYMPUS fear the most. Apparently, despite being the youngest dorm head, she actually exhibits such power that she has killed three Servants on her own, while her Invoker provided only back-up. A quick-to-anger individual that others should be vary of.
She is a prodigy mage, wielding a family-heirloom weapon that is so famous amongst Finnish magi that it is usually kept in the dungeons of Turku Castle, as it tends to accidentally rip through concepts weaker than it. Known for her bad temper and foul-mouth, no doubt herited from her mother who is the Major-General of HADES, Octavia Julmakäsi. Feared woman known as the "Iron Queen of Underworld". Tessa herself was never allowed to enter to the "Wandering Mountain", actually, as she has a presence that disturbs magecraft. A rare form of "Breathing & Walking" where she actually breathes harmful prana. Has made other magi liken her to a wild dragon. A list of campaigns against magi of the Middle-East show that she is quite used to battles. It was thanks to her experience and pure, raw talent that she was chosen as the dorm head of Sea of Estray.
She is said to have the greatest Prana reserves of all the Dorm Heads.