Eye Color: Gray
Hair Color: Green
Age: mid 30's
Affiliations: Adepts
Maria: Unknown
Element: Chlorine
Likes: Torture
Dislikes: Teresa Beria

Known as Gas Chamber, he is a tall, wicked-looking member of the Adepts, and as a Qwaser he wields the element of chlorine, with which he can create noxious and lethal gases or, in conjunction with water, generate hydrochloric acid. He was the one responsible of the massacre that left Teresa as the sole survivor, and years later appeared again at St. Mihaiolv, ordered to complete an "ethnic cleansing" of its inhabitants, namely Sasha, Teresa, Mafuyu, and Tomo. He himself is a psychotic assassin, bent on spreading atrocities such as rape and slaughter in the name of extermination, as he did during the massacres of the Yugoslav Wars.

Croa is a slender wicked looking man, who has spiked up green hair. He is usually seen wearing a lab over coat. He also wears glasses, and when taken off, it reveals his eyes to be tattooed horizontal lines going from his eyes, with vertical lines crossing the horizontal lines.

Croa is shown to be very sadistic, as he seemed to enjoy torturing Teresa about what the abuse he had done to her, and her care takers, not showing any remorse in the slightest.

(Source: Seikon no Qwaser Wiki)