The Coven is an entirely new faction of witches. When Coven is enabled, the neutral role "Witch" is the leader of the Coven. The Coven has a unique difference compared to the Impostors, that being the Coven having a source of power that enhances them.
The Necronomicon is an element given to a Coven member after a certain meeting. With the Necronomicon, the holder gains the ability to vent and assassinate. Some roles even have extra buffs when in possession of the Necronomicon.
The Coven Leader is essentially Puppeteer until the possession of the Necronomicon, where they kill normally afterwards.
Judgment: Impostor
The Medusa is essentially an evil Veteran. Bodies will become unreportable after a certain amount of time.
Judgment: Engineer
The Hex Master hexes players. They switch between killing and hexing. Once all living non-Coven players are hexed, they must eject the Hex Master or the Coven wins.
With the Necronomicon, the Hex Master can kill normally every time.
Judgment: Impostor
The Potion Master is a Coven Evil role that has two potions. They have a Reveal potion and a Curse potion. The Potion Master also has a kill button to serve as a Kill button. While not shifted, the Potion Master can only reveal. And then vent, in order to curse.
Reveal Potion: The reveal potion is a potion that reveals the target's role to every Coven member. This is so the Coven doesn't get free assassinations.
Curse Potion: The curse potion is a potion that makes the target kill a nearby player when triggered. The Potion Master will not know if someone is nearby, they just have to guess.
Judgment: Impostor
The Poisoner joins the Coven when Coven is enabled, otherwise stays as an Impostor (Vampire). The Poisoner is just a Vampire with a cooler name. It will work exactly the same with the same cooldowns. So the Vampire will just join the Coven and ditch the Impostors.
Judgment: Impostor
The Conjuror is a Coven Killing role that can place acid traps across the map. Place traps by shifting and unshifting quickly. Acid disappears once it kills.
With the Necronomicon, they have a delay before disappearing, with the delay timer resetting for each kill. The Necronomicon also gives the Conjuror the kill button (which will not reset the acid trap delay).
When a player enters an acid trap, they instantly die to the Conjuror (no lunge). If shielded or protected, kill doesn't occur (acid trap doesn't vanish). If Pestilence enters an acid trap, nothing happens.
Judgment: Impostor