From Lineage 2 Encyclopaedia

Properties

Weapon Mastery
Increases P. Atk. by 8.5% and additionally by 2.
Class	Dark Fighter
Type	passive
Attribute	-
Recast time	0 s
Cast time	0 s
Cast range	0
Classes with same skill	Human Fighter, Warrior, Gladiator, Warlord, Human Knight, Paladin, Dark Avenger, Rogue, Treasure Hunter, Hawkeye, Elven Fighter, Elven Knight, Temple Knight, Swordsinger, Elven Scout, Plains Walker, Silver Ranger, Dark Fighter, Palus Knight, Shillien Knight, Bladedancer, Assassin, Abyss Walker, Phantom Ranger, Orc Fighter, Raider, Destroyer, Monk, Tyrant, Dwarven Fighter, Scavenger, Bounty Hunter, Artisan, Warsmith, Duelist, Dreadnought, Phoenix Knight, Hell Knight, Sagittarius, Adventurer, Evas Templar, Sword Muse, Wind Rider, Moonlight Sentinel, Shillien Templar, Spectral Dancer, Ghost Hunter, Ghost Sentinel, Titan, Grand Khavatari, Fortune Seeker, Maestro

Skill Upgrade

Lvl. to Learn	Skill Lvl.	Description	MP Consume	HP Consume	SP
5	1	Increases P. Atk. by 8.5% and additionally by 2.	0	0	1
10	2	Increases P. Atk. by 8.5% and additionally by 3.	0	0	1
15	3	Increases P. Atk. by 8.5% and additionally by 4.	0	0	3