Blue !! Weakness
Gained by using a specific physical Weapon Skill on the mob. The set of possible weapon skills is based on the time of day the mob was popped or claimed; depending on which period the time of claim falls under, only Slashing, Piercing, or Blunt WS will work.
Effect on enemy:
Greatly enhances drop rate for equipment and weapon(s).
Inflicts Amnesia on the mob. The message displayed in the log will read:
"Your attack staggers the fiend!
The fiend is unable to use special attacks."
Possible Physical Weapon Skills:
Time: 6:00-14:00 - Piercing:
Archery: Sidewinder, Empyreal Arrow, Arching Arrow, Blast Arrow
Dagger: Shadowstitch, Viper Bite, Dancing Edge, Shark Bite, Evisceration
Marksmanship: Slug Shot, Blast Shot, Detonator, Heavy Shot
Polearm: Skewer, Wheeling Thrust, Impulse Drive
Time: 14:00-22:00 - Slashing:
Axe: Rampage, Mistral Axe, Decimation
Great Axe: Full Break, Raging Rush, Steel Cyclone, Keen Edge
Great Sword: Spinning Slash, Ground Strike
Great Katana: Tachi: Yukikaze, Tachi: Gekko, Tachi: Kasha
Katana: Blade: Ten, Blade: Ku
Scythe: Cross Reaper, Spiral Hell
Sword: Flat Blade, Vorpal Blade, Savage Blade
Time: 22:00-6:00 - Blunt:
Club: Skullbreaker, True Strike, Judgment, Hexa Strike, Black Halo
Hand-to-Hand: Raging Fist, Spinning Attack, Howling Fist, Dragon Kick, Asuran Fists
Staff: Heavy Swing, Shell Crusher, Full Swing, Spirit Taker, Retribution
Taken from a post I wrote up on my LS's forums.