Soro Ken (候剣,Soro Ken? lit. Server Sword) is a sword technique which stops the regeneration effect of the samurai body. Any samurai cut by this technique cannot regenerate the body part which was cut (for example, Daruma's right eye in his humanoid form). Samurai are able to apply Soro Ken to their fighting techniques to increase their effectiveness. Ata demonstrated this by adding it to Kongo-Yasha Style: Pack Whirlwind.
Sōrō (候,Sōrō?) means "to serve (by a superior's side)", but when read Sō (候,Sō?) the kanji means "climate", "season" or "weather".
Daruma compares what happened to Benkei's body to the scar over his right eye, implying that said scar was inflicted by a Soro Ken user in the past.[1]