Per the Wiki, having Mask of the Penitent on means you cannot be afflicted with Defiler Poison.
Unnum still got afflicted with Defiler Poison from doing Alchemy experiments, even with the mask on.
Mask of the Penitent does not prevent Defiler Poison from Alchemy
Re: Mask of the Penitent does not prevent Defiler Poison from Alchemy
Are you actually taking damage from defiler poison? My ES is immuned from it but the status effect will still show even though he's not affected by it.
Re: Mask of the Penitent does not prevent Defiler Poison from Alchemy
Yes, he was taking damage from it.
Per the skill description, it explicitly will not remove pre-existing instances of the poison. So it's supposed to be possible to have the status effect with the mask on, and by implication take damage from it. It's just you're not supposed to be able to get the status effect while the mask is on. Per the Wiki, anyway.
And yes, he turned it on before starting on alchemy experiments.
Per the skill description, it explicitly will not remove pre-existing instances of the poison. So it's supposed to be possible to have the status effect with the mask on, and by implication take damage from it. It's just you're not supposed to be able to get the status effect while the mask is on. Per the Wiki, anyway.
And yes, he turned it on before starting on alchemy experiments.