Perhaps ancestral magic is the only way to stop the poison since the ancestors' intention was to destroy the Mikaelson by limiting their sources of healing to nothing, perhaps the only magics strong enough would be Silas or Hollow if they were to stop themselves, the bite, or some strong witch like Freya or Vincentt channeling any of the three magics for this purpose, because "low / medium" magics of traditional witches or siphons would not be enough.
