Koshi Serpent

What initially appeared to be many serpents is in fact a single creature, consisting of eight snakes fused together. The immense tail of this creature ends in a mighty, sword-like blade.

Monster Encyclopaedia II: The Dark Bestiary
Author J. C. Alvarez
Series Monster Encyclopaedia
Publisher Mongoose Publishing
Publish date 2005

Koshi serpents are demonic ophidians, probably related to hydras. A koshi serpent appears as a huge jade snake with eight heads, whose single tail ends in a clanging blade resembling an oversized greatsword.

Koshi Serpent
Huge magical beast
Hit Dice	9d10+45 (94 hp)
Initiative	+7
Speed	30 ft. (6 squares)
AC	20 (-2 size, +2 Dexterity, +10 natural), touch 10, flat-footed 18
Base Attack/Grapple	+9/+24
Attack	Bite +15 melee (1d8+7 plus poison) or tail slash +14 melee 4d6+7/19-20)
Full Attack	8 bites +15 melee (1d8+7 plus poison) and tail slash +12/+7 melee 4d6+3/19-20)
Space/Reach	15 ft. /10 ft.
Special Attacks	Poison
Special Qualities	Darkvision 60 ft., Low-Light Vision
Saves	Fort +11, Ref +9, Will +4
Abilities	Strength 24, Dexterity 17, Constitution 21, Intelligence 4, Wisdom 13, Charisma 7
Skills	Listen +7, Spot +7
Feats	Combat Reflexes, Improved Initiative, Multiattack, Weapon Focus (bite)
Environment	Any desert
Organisation	Solitary
Challenge Rating	7
Treasure	Standard
Alignment	Usually neutral evil
Advancement	10-18 HD (Huge), 19-27 HD (Gargantuan)
Level Adjustment	+5 (cohort)

Combat

Koshi serpents may wield their sword-shaped tails just as if they were real swords. The swordtail of a koshi serpent counts as a secondary attack when used in conjunction with its bite attacks, though it allows a second attack at a -5 penalty when used as part of a full attack action.

Poison (Ex): Injury DC 19 (Constitution based), initial and secondary damage 1d8, Strength.