The Lord is the most powerful unit on the map, several times stronger than a swordsman. If he is killed, then it's game over for the player, and all his buildings, units, and civilians will instantly disappear from the map. The lord can be commanded around, but he will wander his castle at times, then return to the keep during siege.
During campaign missions in both Stronghold and Crusader, the Lord cannot be freely controlled. He may be ordered to attack any enemies accessible, but he cannot be moved over the map. In multiplayer and skirmishes, however, he may be moved. This can be useful, as you may seek refuge in your more powerful ally's castle (you cannot win through keep capture in SH and SHC). When selecting units through the click and drag technique, the Lord won't be included in the group of troops.
In Stronghold 2 and onwards, the Lord becomes a much more important unit as a fighter. Literally, the Lord has become a powerful knight, who is the only unit to mount horses besides knights. As usual, the Lord will stand on the keep's roof and attend events in the town. However, when moved to another location, the Lord will enter 'combat mode' and he stops taking part in feasts, masses, etc. He may be returned to do his civilian duties with a button click at any time. The Lord is now selected, when click and dragging over him.
In the latter games, the Lord can be healed in the Apothecary, when he lost more than half of his health. This action can be performed, when he is doing his civilian duties.
If u want to put your lord in seige so then the following requirments must be done:The lord must be guarded by 2 or more knights and be put in the back of the seige.