Dao is a category of single-edge Chinese swords primarily used for slashing and chopping (sabres), often called a broadsword in English translations because some varieties have wide blades. Dao also appears in the names of such polearms as the pudao and guan dao, indicating that their blades were primarily intended for slashing and cutting attacks rather than stabbing ones.
Li Mei uses a modified dao called a Kunlun Dao in Deception and Armageddon. Appearance-wise, it looks similar to a double-edged short sword with a thin blade.
Dairou also uses his own modified dao, which he refers to as the Autumn Dao, in Deception and Armageddon. The dao differentiates from most by not only having larger blade but also having serrations on its edge and spine near the tip.
Shujinko uses a modified two-handed dao, quite similar to a dadao, named a Dan Tien Dao in Deception and Armageddon.
There's also a similar sword to Shujinko's Dan Tien Dao called a Quadspade located in Liu Kang's Tomb, presumably belonging to Liu Kang or was left there in honor of him as a gift.
The Red Dragon Sword in the Chamber of Artifacts is in fact a Lungchuan Dao which was incased in a large crystal, that can be broken in order for kombatants to use. It was a large two-handed sword.
Graff, David A. (2002). Medieval Chinese Warfare, 300-900. London: Routledge. ISBN 0-415-23955-9.
Grancsay, Stephen (1930). "Two Chinese Swords". The Metropolitan Museum of Art Bulletin, Vol. 25, No. 9, pp. 194–196
Tom, Philip M. W. (2001). "Some Notable Sabers of the Qing Dynasty at the Metropolitan Museum of Art". Metropolitan Museum Journal, Vol. 36, pp. 11 + 207-222
Tom, Philip with Scott M. Rodell (February 2005). "An Introduction to Chinese Single-Edged Hilt Weapons (Dao) and Their Use in the Ming and Qing Dynasties". Kung Fu Tai Chi, pp. 76–85