The Twins work similar to the Sorcerer and the Inquisitor, both will always spawn together. The Evil Twin is a neutral killer who must kill everyone opposing him (same win condition as possessor or reaper), however unlike the inquisitor who counters the sorcerer, the good twin supports him. They must work together in order to achieve their goal.
The Evil Twin
Neutral, Killer
Win condition
Kill the BD, Cult/Unseen and anyone who opposes you.
Passive 1: Special Bond
You and your twin can communicate at night. If your twin dies at night or is executed by the prince, his killer will be revealed to you.
Passive 2: The Evil Gene
You are immune to death at night.
Night ability 1: Slash
Kill a player. Infinite uses.
Night ability 2: Psycho protector
Protect your twin tonight, healing any poison or bleeding effects on him and making him night immune. Everyone who visits your twin tonight will die. 3 uses.
The Good Twin
Neutral, Support
Win condition
You win as long as your twin achieves his goal, even if you are dead.
Passive 1: Special Bond
You and your twin can communicate at night. If your twin dies, you die as well.
Passive 2: The Good Gene
You are immune to occupation. You will appear as BD to investigative results.
Day ability 1: Swap
Swap places with your twin for the rest of the game. Cannot be used if you or your twin are on trial. 1 use. (This is similar to possessor jump, since it changes both twin’s names and positions.)
Night ability 1: Cleanup
Make your twin occupy immune and hide his visits from investigators. 3 uses.
Night ability 2: Smart Protector
Heal your twin from any poison or bleeding, and occupy anyone trying to visit him. 3 uses
Description: The evil twin is a neutral killer that might not be as powerful as other neutral killers by himself, but he always spawns with the good twin, which supports him and helps him achieve his goal. The twins can speak at night in order to plan their next move. If the evil twin is under suspicion, the good twin can swap places with him so he is killed or executed instead of his brother. If the good twin dies the killer will be revealed to the evil twin, this makes the prince think twice before executing the good twin since he will be revealed to his brother.
Note: If the evil twin becomes king, he will turn into the Psycho King. If the good twin becomes king, he will become a Neutral King, but his win condition still involves helping his twin achieve his goal. Both of these kings can still speak to their brother at night and the good twin will still commit suicide if his brother is killed.