Siegfried is one of several exclusive units in Stronghold Legends, and cannot be purchased by any faction. Siegfried is based upon the legend of Siegfried of Xanten.
He is exclusive to the Ice faction, and is only used in a small number of official game campaign missions where he substitutes Dietrich as the Lord, or compliments him.
There is no way to use Siegfried within a Custom Skirmish or multiplayer game, although he is available as a computer opponent.
You can however place Siegfried as your Lord within a custom map using the game editor, overriding the default game behaviour to use Dietrich, but this will only work if you are playing as the Ice faction.
The Lord is the single most important unit in the entire game. He is in command of the entire Castle and is equipped with a weapon to defend himself should he be confronted with enemy units.
Should the lord die, the game will end so for this reason it is vital to protect him well. The health of your Lord cannot recharge over time. If he is injured, then these injuries will remain for the rest of the game.
Like all Lords, Siegfried has a special power to defend himself with should be be attacked, in his case called Summon Maidens. The Lord special powers are designed to make Lords more durable in attacks and for a certain time will summon "magic" reinforcements to his aid.
In the case of Siegfried, this will magically bring 7 Shield Maidens to wherever you choose on the map. This can be incredibly useful if your Lord is under attack from enemy units and you need immediate reinforcements or bodyguards.
You can activate this special power by left-clicking on the blue trident icon on the right side of your screen, and right clicking on the map where to use it. It can only be used somewhere within Siegfried's range already, and once used, it will require a "recharge" time.
During this, the green line around the outside of the blue trident icon on your screen must reach all the way around to the start before it can be used again. You can use this ability as many times as you would like throughout the course of the game.
Once summoned, the Shield Maidens will appear in the game for a certain amount of time and will have exactly the same characteristics as normal Shield Maidens. They can be killed in the same way regular Shield Maidens can.
Note that if this happens, it does not affect how many Shield Maidens you summon from this special ability in the future, it always remains the same consistent amount. Once the time has elapsed, the Shield Maidens will automatically disappear from the map regardless of where they are located or how much damage they have sustained.
The Lord is also one of only a few units that can fight mounted on horseback, or dismounted on foot. You can mount the Lord by left clicking on the "Mount horse" icon when the Lord is selected. You can dismount him from his horse by selecting him and then clicking on the "dismount" icon.
Once mounted on a horse, any enemy units must first kill the horse before they can attack Siegfried himself, so there are great advantages of doing so, besides Siegfried moving a lot faster. The horse alone takes 2 Crossbow bolts to kill.
If the Horse is killed or you dismount Siegfried, you can mount Siegfried on another horse, but must wait for a short "recharge" time before this button becomes available again. To do this, select Siegfried and then click on the "Mount horse" icon.
Note that by mounting Siegfried, like any unit, it will cost 20 Honour. Once you have attempted to mount him, a horse will instantly appear and he will automatically be mounted.