The 903rd Chemical Tactics Troop (abbr. 903-CTT) is one of the secret units known as 'The Invisible 9', which were developed from the work of Dr. Kauplan. They are also known as "Krankheit Jäger"(Disease Hunter) and 'Harbinger of the Ashes of Death' (死灰を撒く病兵).
These troops, for which Wolmarf was a leader, are specially-trained in the use and deployment of chemical and biological weapons, many of them banned by international convention, but were developed and used secretly during the war. After the war, however, the troop became bandits and called themselves 'Grey Wolf'. They looted whatever village they happen upon, sometimes using the weapons at their disposal against the defenseless people, either to clear them out, or just out of spite. About 2 years from the cease-fire, they settled around a dam and made it their home, extorting supplies from a nearby village.
The 903rd C.T.T. specialized in using bio-chemical weapons. Their chief specialty was the compound Kirche-3 which is an airborne chemical weapon, deployed using an aerosol shell. Those with strong immune systems are not affected by it. It can cause high fever, memory loss and more within five to six hours, especially to those who are suffering from malnutrition. Those who are affected will die in twenty hours if not given the antidote.