Primum Nil Nocere is a specialized activity and task that can only be completed during the side quest The Thunderstone (
The Thunderstone). It involves using your medical skills to heal a villager in exchange for a quest item.
If you're interested, Primum Nil Nocere is Latin for "First, cause no harm."
Starting the Task
While searching for the artifact during The Thunderstone, you will meet Mlada in the village of 
Suchdol.
She possesses the stone but will only part with it if you help heal her husband, Peter, who is gravely ill. Agreeing to help her begins this task.
Diagnosing Peter
Peter is lying in bed inside Mlada's house. To determine what is wrong, you must examine him:
The symptoms: Mlada explains he is restless, won't eat, and normal medicine has failed.
Examination: Speak with Peter and ask all available questions. You can perform physical skill checks:
- Strength check (Easy): Examine him by touch.
- Vitality check (Hard): Observe his physical condition.
- Agility check (Hard): Check his reflexes.
Regardless of the skill checks, you will determine that Peter is suffering from extreme anxiety and fear, rather than a physical disease.
The Treatment
The primary cure for Peter is a Chamomile Brew.
You need Sage and Chamomile. If you don't have them, they can be purchased from the Grocer in Suchdol. The nearest brewing station is located in Suchdol fortress.
The Chamomile Brew is also purchasable from any better Apothecary, like the one in Kuttenberg. Give the brew to Peter.
To ensure the best outcome and extra XP, use any other available skill-based options:
- Pray for him (Hard speech check).
- Offer advice on dealing with fear.
- Change his diet (Medium Scholarship check).
- Cast a spell (Very hard speech check).
Primum Nil Nocere Completion
After administering the treatment, you must wait one full in-game day for the effects to take hold. Skip time or go to sleep in Suchdol. You can also do the White Roebuck side quest (The White Roebuck), which is nearby.
Return to the house and speak with Mlada. She will be overjoyed at his recovery and hand over the Thunderstone.
Rewards:
- The Thunderstone (required to progress The Thunderstone side quest).
- Scholarship XP and Survival XP.
This finishes the Primum Nil Nocere task in Kingdom Come: Deliverance 2 and allows you to wrap up The Thunderstone too.
Primum Nil Nocere FAQ
When can you start this task?
Only during The Thunderstone when you meet Mlada in southern Suchdol and agree to heal Peter.
What item heals Peter?
Chamomile Brew from Sage and Chamomile, or buy it from an apothecary in Kuttenberg.
What is wrong with Peter?
Extreme anxiety and fear, not a physical illness. All examination checks confirm this.
How long is the wait?
One full in-game day after the brew. Sleep or skip time, then talk to Mlada.
Can you skip The Thunderstone quest?
Stealing the stone from Mlada skips both the side quest and this task. See our Thunderstone guide.