The Dark Horse has a black body with a white face and scars as well as wounds all over its body. Its eyes are red. If it dies, the Dark Horse respawns after an in-game delay. If the player's honor becomes neutral or good, the Dark Horse does not respond to the whistle, even if it has been saved at a hitching post. The Dark Horse can run through the brush and other off-road places without a drop in speed, unlike other horses.
Setting up a campsite then traveling from it may glitch the Dark Horse, losing its saddle and acting like a wild horse. When the player whistles, a saddled Dark Horse appears.
The player will receive the following message after earning the honor level of Road Agent, thus receiving the dark horse: "Your honor has dropped low enough that a dark horse has responded to your whistle. If your honor goes back to neutral or above, you will lose this rare mount."
The Dark Horse is not the same color of black as the War Horse. It is actually a minimally expressed American Paint Horse (minimally expressed means there is a very small amount of white, such as across the face).
Due to its powerful and chunky build, it could possibly be a type of draft horse, which are horses used for manual labor.
If the Dark Horse is used in a mission where another character has to be followed on horseback, depending on how fast the character rides, the Dark Horse will not be able to keep up. It is a good idea to either break a wild horse or, being with low honor anyway, steal a horse before beginning such a mission.
Sometimes a glitch occurs, and when the horse is called, two come. This also occurs with the War Horse.
A good way to keep the dark horse is to put on the bandana so that positive actions don't increase the player's honor.
This mount is considered rare because the player can only obtain it by having a very low honor level.
In Tumbleweed, scrawled onto the altar in the church is "the Devil has gotten into that beast," possibly referring to the Dark Horse.
This is the only horse you get by being bad.
If you abandon the horse and break, and/or hitch any other horse regardless of what it is, if you whistle for it, another dark horse will respawn.
If you kill the dark horse and wait awhile, you will receive another dark horse.
If the player is wanted, the Dark Horse's ability to run off-road without a drop in speed allows the player to quickly lose their wanted status.
The player can skin the Dark Horse.
The Dark Horse is possibly a reference to the 2007 remake of "3:10 To Yuma", where the Mexican sniper member of Ben Wade's gang rides the horse during several brief scenes.