The downside of the witch's poison is that the doctor has an increased chance of resurrection, meaning two nights instead of one...
The necromancer has a random boost - zombification/resurrection.
The black wizard has 50% block as a special ability - it cannot be increased (for example, if a wizard and a black wizard are left, neither of them will win - because the black wizard cannot kill the wizard, and the wizard cannot hang the black wizard).
1) increases the combat effectiveness of the city and the confidence of the owner of a specific role.
2) adds a new scenario/outcome.
The black wizard has poison as a special ability, not in the neutral deck. This is a way of self-defense.

Барон "Vampires"
Отдай свои прошлые сны,
В сомненьях себя обрети,
В бешеном танце душа кружится!
Не думай, что будет потом,
Здесь и сейчас мы живем,
Стань хоть на миг сам собой, слышишь!