Lions are dangerous as they effectively attack almost any human in the game, from soldiers to peasants, workers to civilians. They also like to go after deer and Camel herd (Though lions only attack camels when encountered unlike deer in which they chase). They breed when not moving, making them particularly dangerous.
They tend to be very durable and vicious in combat, and they will run to the victim to quickly close distance. They attack in small groups and they are able to kill an assassin or a maceman on their own.
Lions can be simply killed by any soldiers in close combat or projectiles. Fire will also fry lions in no time.
There is an event called 'Lion Attack', which can be called customly in Castle Builder and predefined in custom missions. It spawns a number of lions randomly on a map, which aggressively head for the player's castle to terrorize peasants and units. It also causes a popularity dropdown to 80 and -2 monthly popularity until the lions are killed or 6 game months have passed.