(POV: Lumiere)
Antibiotics...
In medieval times it'd be a significant advancement in healthcare.
Good knowledge of microbiology and medicinal properties were required to identify natural substances with antimicrobial properties.
For instance, experimenting with plant extracts like— garlic, honey, or herbs, known for their potential antibacterial or antifungal characteristics.
Devising methods to isolate and concentrate these beneficial compounds, potentially using distillation or extraction techniques.
The resulting formulations could be applied as topical treatments or administered orally to combat infections.
Anyone who was capable of doing all this could never be from this age.
It was simply impossible...
My guess... they're an Integrator.
There's no way news like this would've slipped under my nose if I was still as frequent in the kingdom.
If I'm being honest, staying in the Silva Citadel basically meant isolating yourself from the entire kingdom.
