Starting stats and subclass
The official wiki recommends starting with VIT 3, INT 3, STR 4, and DEX 6. At level 5 you choose a subclass:
- Blade-Fight Force: stealth and precise melee attacks with the dagger.
- Archery Force: ranged attacks with the bow.
The Blade-Fight tree is built around getting in, hitting hard, and disappearing:
- Ambush: ambush your enemy.
- Fast Attack: approach an enemy fast and make a deadly attack.
- Rolling Dagger: whirl around enemies with a dagger.
- Stealth: hide yourself.
- Poisonous Cloud: poison the area around the enemy and intoxicate them.
- Insidious Poison: temporarily disappear before the attack.
- Astral Light: the capstone skill of the tree.
- Ambush Boost: increases the attack power of Ambush.
The Archery tree focuses on arrows, mobility, and area pressure:
- Arrow Shower: shoot several arrows at several enemies.
- Feather Walk: make your body lighter to increase moving speed.
- Fire Arrow: ignite the arrow.
- Poison Arrow: coat the arrow with powerful poison.
- Repetitive Shot: shoot several arrows at an enemy.
- Spark: inflict damage with a beam of light.
- Storm Shot: a heavy ranged shot.
- Fire Arrow Boost: increases the attack power of Fire Arrow.
Skills can be raised to level 20, with a chance to master at 17. Community skill guides recommend mastering Ambush, Rolling Dagger, and Fast Attack first, since they all hit groups of monsters. Ambush and Fast Attack are the main damage dealers, and Rolling Dagger adds poisoning on top. After that, the choice is between Stealth and Poisonous Cloud, which are built for PvP.
A common PvP combo is Stealth into Ambush, or knocking the enemy back and hitting with Rolling Dagger up to three times.
Weapons
Daggers have low attack values until about level 65, then they rise sharply, and they hit very fast to make up for it. For PvP, piercing stones on daggers help ignore defense. The bow is mainly a PvP and polymorph tool: community guides note that ninjas are the best class for polymorph because the bow has the highest attack value in the game, and a polymorphed ninja can kill higher level bosses.
Source
[1] Metin2 Wiki (Gameforge): Ninja class overview and skill list
[2] Metin2 Wiki: Dagger Ninja skill guide