The Witcher blade enhancement

Blade enhancements (or weapon upgrades) include oils, temporary and permanent runes, and a few other items found in the game. Meteorite ore is included (for completeness) but it is more of a blade replacement. Also note that only one oil or temporary rune can be active at a time; effects do not stack (i.e. the new application removes the previous one).

Other (used individually)
Schwertaufwertungen Ενισχύσεις σπαθιών Objets d'amélioration des glaives Potenziamenti per le spade in The Witcher Ulepszenie broni w grze Wiedźmin