Race: Fiend
Rank: Tentacle Demon
Debut: Ninja Gaiden (Xbox)

Hydracubus is a servant of the Greater Fiend Marbus, and a reoccurring sub boss in Ninja Gaiden. It is one of the easier bosses with predictable patterns.


A giant Tentacle monster with eyes throughout its body. It has two large main tentacles and a large mouth at the top of its body.

Abilities and PowersEdit

Tentacles & Regeneration: While Hydracubus is covered with tentacles, it only has two longer tentacles at a time that are useful for combat. These longer tentacles regenerate back when chopped off. However, this takes time, during which Hydracubus is vulnerble without its two long tentacles. Given the chance, it will grab victims with its tentacles and swallow them alive.

Fireball Meteor: When vulnerable, angry or frustrated, Hydracubus with spit out fireballs into the sky, that fall back down and randomly land in a radius around Hydracubus. The accuracy of this attack isn't good.


Ninja Gaiden: Early during the Dark Dragon Blade Incident, Ryu Hayabusa had encountered Galla Fiends in combat for the first time. After Ryu slayed the fiends, Rachel, having witnessed the battle from on top of a Monastery wall where she was sitting, began showing interest in the young Dragon Ninja. During their conversation, Hydracubus appeared, breaking through the wall, grabbing Rachel with one of its tentacles and swallowing her. Then it proceeded to attacking Ryu, but the Super Ninja was more than it could handle, and too quick for it's tentacles. With agile speed and precision attacks, Ryu killed Hydracubus, and saved Rachel.

Later, while Ryu was battling Fiends in the arena of Marbus's Fiend Realm, during one of the rounds, the Greater Fiend Marbus summoned Hydracubus. Again it tried swinging it's huge arms around, and covering the area with falling fireballs, but Ryu was too quick, dodging it's attacks, cutting off it's arms and destroying it's main body again.


  • Hydracubus is one of the easier bosses, if not considered the easiest boss in the game.
  • Use the Flying Swallow on his two large tentacles until both are cut off. Since the tentacles will always release blue essence, heal yourself with the first and when the second is cut off, do a full charge Ultimate Technique to quickly unleash a flurry of attacks on it while it's vulnerable.
  • When it grows its arms back, repeat this pattern of chopping off it's tentacles and attacking it's armless main body again, until it is defeated.
  • In Ninja Gaiden Black and Sigma they are accompanied by Lesser Fiends. Take care of these first so they don't become a nuisance.


  • Hydracubus's name is a cross between a Hydra and a "cubus" sex demon (Incubus & Succubus).
  • Hydracubus is a reference to Japanese Tentacle Rape Demons, having been introduced attacking Rachel and covering her with its slime, typical traits of Japanese Tentacle Rape Demons.

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