Non-Invasive Procedure is an achievement of Baldur's Gate 3.
Involvement[edit]
In the House of Healing found within the Shadow-Cursed Lands of Act II, the party can encounter Malus Thorm and four sisters performing surgery upon a helpless victim within an operating theatre.
To get the achievement combat must be initiated, so convincing Malus to allow the sisters to perform surgery on himself, thereby killing him without combat, does not work.
In combat, the sisters can stun and hold party members allowing Malus to perform surgery, therefore it is best to eliminate them first, preferably before entering combat by convincing Malus that the sisters need to improve their surgical skills on one another.
During combat, Malus attempts to resurrect the sisters by touching them, so holding or immobilizing him is a good strategy.