Total War Encyclopaedia

The ninja acts as an assassin, spy, saboteur and scout and is recruited via stealth buildings. In addition to their subterfuge skills, ninja also increase the movement of and prevent the demoralisation of your armies when placed inside them. They can also establish spy networks within your own castle towns that increase the distance you can see into a neighbouring province and decrease the likelihood of rebellion. Ninja are invisible to the enemy unless detected.