Karasu Tengu is a person who wears a Knightmare giving him the power to manipulate wind, float and fly for short periods of time. He has several holes throughout his body that act as vents for his powers and bears the same variation of the Black Knights insignia used by the unnamed individual who resembles Lelouch on his chest. Andreas Weinberg describes him as someone who is "human, but not human at the same time".
Karasu Tengu first appears at the Jesuit base, where he destroys the roof and kidnaps Claire le Britannia. He appears once again terrorizing a local village in order to create a vacated place where he waits for a ship to pick up Claire. Andreas points out that there must be a limit to how long he can remain in flight because of this.Karasu Tengu is named after the Tengu of Japanese folklore. They were usually anthropomorphic bird demons or monsters associated with war. Source: CodeGeass Wiki