The term “Witcher” comes from the Slavic word vytynátse, which means “he who makes his way by intuition.”
Witchers are trained in specific schools that teach them how to track and kill monsters. They are also taught how to use alchemical mixtures known as potions that enhance their physical abilities and give them other useful benefits. Witchers have superhuman strength, speed, agility, and reflexes. And they are also able to sense danger, fight without limits in close combat and use magic signs (spells).
Witchers are sterile because they have been mutated with mutagens that affect their reproductive systems as well as other organs in their bodies. These mutagens make it so that they cannot reproduce with humans or even each other — only with elves or dwarves could they have children but these are extremely rare cases.
Witchers age slower than regular humans. They reach maturity at 20 years old, but they can live up to 200 years old if they aren’t killed before then.
Witchers use steel swords and silver blades; their swords are crafted from special steel that has been magically hardened (not an alloy) with dwarven runes etched into the blade by a master blacksmith who uses ancient techniques passed down for centuries (The Steel That Won the North). Their silver blades are made with the same techniques as their steel swords but with silver metal instead of steel metal (The Silver Sword).