Viridiana offers the Penitent One help with some boss fights. She can only assist the Penitent One with three of these fights. If assented to, Viridiana will be present during the boss fight and will heal the Penitent One on low HP. This healing requires some time to trigger, so it will be canceled if the player immediately heals himself with a Bile Flask. Viridiana is never targeted or damaged by boss attacks.
Viridiana appears increasingly older each time when her assistance is used. She will die after the third fight, granting the player the Last Breath Achievement. The player can keep Viridiana alive by refusing her assistance or simply ignoring her whenever she appears.