The Red Devil Cartel are one of the factions of Rebel Galaxy, once you start the game you will have a slightly hostile reputation with them, which means you will be on a bad foot with the Red Devil Cartel.
This isn't as bad of a reputation as those you have with the other starting factions, so it gives you an easier window to get into a good stand point with the Red Devil Cartel, who, are one of the few opposing factions of the System Militia.
The best way to join the Red Devil Cartel is to get to a part in the main story where your mission requires you to meet Juster, once you hail him you should join him and later on back stab the Militia. Destroy all Militia ships and fighters, including Zenya. This will give you a significant boost in reputation with the Red Devil Cartel.
The Red Devils are known to fly a variety of ships, from the common Mastadon light frigate to the imposing Blackgate dreadnought. One possible name of a dreadnought is "Red Devil Gargantua".
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