There’re 3 main types:
Locust Stone: Obtain from Quest. You must finish Cruel Tuan Quest to have a Locust Stone.
You must complete Dead Valley Quest at Master Zhao, Da Li (Level 20). Then do quest Cruel Tuan, you can receive Locust Stone!
Plum Dart: Exchange at Leila, Lou Yang(117,184). Using 50 Magnificent Jade exchange 1 Plum Dart.
Plum Dart
Magnificent Jade is found at Quest 1,2,3 Kroraina ( Golden Chain, Buddha Bead, Lava Field ).
Ice Needle: Using x20 Ice Star Scraps at NPC Grand Chien, Kroraina (131,117) to exchange Ice Star Stone. Using Ice Star Stone + Plum Hill exchange Icy Needle.
Ice Needle

How to use Hidden Weapon?
At Green Yim, Luo Yang (111,201).
Choose Learn Hidden Weapon techniques to learn skill Hidden Weapon.
Hidden Weapon Cast
✔️Condion: Level Weapon = 40
✔️Weapon learn one of the following skills:
Every 3 seconds create once damage to an opponent by a certain number of points, within 15 seconds.
Increase one of the point: Phy. Atk, Spi. Atk, Ice-Fire-Thunder-Poison Atk,.. give yourself a certain number of points.
Hidden Weapon Seal
✔️Condition: Level Weapon = 70
✔️Weapon learn one of the following skills:
Ties up your target within 6 seconds.
Make your target dizzy within 10 seconds. Interrupted by any attack.
Decrease your target’s movement speed by 50% within 10 seconds.
Decrease Phy. Atk – Spi. Atk your target a certain number of points within 30 seconds.
Hidden Weapon Defense
✔️Condition: Level Weapon = 90
✔️Weapon learn one of the following skills:
Increase one of the point: Phy. Atk, Spi. Atk, Strength, Intelligence, Stamina, Wilpower, Agility,… give yourself a certain number of points.

-Reset Hidden Weapon Attributes:
Refreshing the attribute is use that attribute point to exchange the different attribute point ( Point added random ).
In order to reset Attributes, you use Divine Stone

-Reset Hidden Weapon Skills:
If you aren’t satisfied with the skills your hidden weapon obtains. You can use an Oblivion Stone to reset the skills.
Note: All the skills of your hidden weapon will be reset.

-Reset Hidden Weapon Grade:
Using Sacred Jade or Super Sacred Jade to reset the grade of your Hidden Weapon.

-Reset Hidden Weapon Practice Level:
Using Fiery Stone to reset practice level of a Hidden Weapon to Level 1.
Note: Enhancements, inscriptions, gems, grade, aptitude won’t be affected.

Dragon Oath II - A new journeys.