This is another player home DLC. It is also known as the Fighter’s Stronghold. Except this is a castle and has 2 quests involved with the castle. To get this castle, you will receive a quest that tells of that there is a castle under siege by some marauders and that their leader has died, so the castle will go to whoever can break the siege.
The castle is near the city of Chorrol, and you will get a map marker for it. Once you arrive, you will find 3 marauders and 1 marauder warlord. You will also find the corpse of the recently deceased Lord Kelvyn, the former lord of Battlehorn Castle and leader of the True Horn, a group of knights. Once you kill the marauders, either one of the knights will approach you or when you talk to one of them, they will give you Lord Kelvyn’s will which basically gives you ownership of the castle, and direct you to Nilphas Omellian residing in The Merchants Inn at the Imperial City, Market district.
Once you purchase everything from Nilphas, he will send a letter to one of your men of arms to say he has a functional dwemer forge for sell. Once you buy it, it will be installed at your blacksmith area. Going near it will temporary boost your armorer skill by 15 points.
There is however, a second quest but it is unmarked. It can be started when you find the movable pillar in your private quarters and reading the journal of Kelvyn’s father; Lord Jaren. His journal tells of what happened to the original lord of Battlehorn castle and their leader of their knight faction. It reveals the location of the castle’s hidden grotto.
You can go to the grotto (hidden in the training room) to kill Lord Kain to free him and the lich (a necromancer who ascended). Other than that, there is no other quest.
There are interesting npcs whom reside in the castle however. You have an Orc (Shagrol gro-Uzug) whom you can spar with in the training room, a personal taxidermist (Melisi Daren) whom if you provide the material will create the stuffed animal/creature and display it in the great hall, a personal cook whom provides a selection of food and wine (Plautis Rusonius), a captain to lead your Men-at-Arms (Castellan Athon), a man whom tends to the wine-cellar and is able to brew special combat-enhancing wine to aid you (Talan) who also happens to be the brother of the famous wine-maker Tamika (who resides in Skingrad) and finally your maid whom resides in your private quarters (Rona Benanius).
There is also a mod that makes Battlehorn castle compatible with COBL and allows it to use COBL related features. I think the castle is rather bland personally. I didn’t particularly like the castle although the back-story about the castle, the True Horn knights and their leaders was interesting. But it just lacked life and felt way too empty for me overall.