Your time patching up the injured has allowed you to know what to carry and have it when needed to keep your allies in one piece.
Requirements: Level 4+, INT or WIS 15+, proficiency with Medicine, and Herbalism Kit.
Your Medicine skill will use INT or WIS whichever is highest
You gain expertise with the Medicine skill.
You may spend 3 hours and 30gp to upgrade a “Healer’s kit” to a “Doctors Bag”. A Doctors Bag acts as a Healer’s kit, but has 20 charges and regains 1d10 charges/hour of down time spent refilling your Doctor Bag.
The Good Doctor: The “Healer feat” feature “Battle medic” now heals up to 1 Hit Die + your Medicine modifier + proficiency bonus when using your Doctor Bag in place of a Healer’s kit.
Surgical Expertise: You may expend 4 hours and 10 charges of your Doctor Bag to attempt surgery (DC20 Medicine). This could be to reattach a lost limb or appendage, remove a foreign object from the body, etc. On a failed attempt you can not use Surgical Expertise again until you complete a short or long rest.