You treat one or more patients’ wounds, attempting to hasten the healing process.
You must perform this action over the course of a Long Rest. If you and your party spend 3 Watches (12 hours) taking the Long Rest, you gain the benefits of the Long Rest. If your party only spends 2 Watches (8 hours) on the Long Rest, then you don’t have enough time to treat your patients and also get a proper rest, and so you do not gain the benefits of the Long Rest.
If you and your party spend an entire day resting, you can perform this action once between Long Rests. Your patients can still only benefit from one Long Rest per 24 hours, however.
Make a Medicine Lore check, with a -2 Penalty for every patient after the first that you are attempting to treat, against a DC of 20. You take an additional -4 Penalty to your check per patient suffering from the Venom condition.