[DracoDei]

There are probably still some copy-pasta errors and typos in this, and I haven't estimated the CRs yet, but I am going to go ahead and post this (especially since I know that many of you are probably looking forward to the entries in this series).
Sinister Spinal Cords
Open Spoiler below for main stat block for Fine through Small sinister spinal cords.

Spoiler

~	Sinister Spinal Cord, Fine	Sinister Spinal Cord, Diminutive	Sinister Spinal Cord, Tiny
Size and Type	Fine Undead	Diminutive Undead	Tiny Undead
Hit Dice	1/16d12 (1 hp)	1/8d12 (1 hp)	1/4d12 (1 hp)
Speed	15 ft. (3 squares), climb 15 ft., swim 15 ft.	15 ft. (3 squares), climb 15 ft., swim 15 ft.	15 ft. (3 squares), climb 15 ft., swim 15 ft.
Initiative	+10	+9	+8
AC	24 (+6 Dex, +8 size); touch 24; flat-footed 18	19 (+5 Dex, +4 size); touch 19; flat-footed 14	16 (+4 Dex, +2 size); touch 16; flat-footed 12
BAB	+0	+0	+0
Grapple	-21	-16	-11
Attack	(Paralysis Attempt +14 Melee Touch)	(Paralysis Attempt +9 Melee Touch)	(Paralysis Attempt +6 Melee Touch)
Full Attack	(Paralysis Attempt +14 Melee Touch)	(Paralysis Attempt +9 Melee Touch)	(Paralysis Attempt +6 Melee Touch)
Space/Reach	1/2 ft./0 ft.	1 ft./0 ft.	2 1/2 ft./0 ft.
Special Attacks	Paralysis, Strangle	Paralysis, Strangle	Paralysis, Strangle
Special Qualities	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits
Saves	Fort +0, Ref +6, Will +2	Fort +0, Ref +5, Will +2	Fort +0, Ref +4, Will +2
Abilities	Str 1, Dex 23, Con --, Int --, Wis 10, Cha 1	Str 2, Dex 21, Con --, Int --, Wis 10, Cha 1	Str 4, Dex 19, Con --, Int --, Wis 10, Cha 1
Skills	-	-	-
Feats	Improved Initiative(B), Weapon Finesse(B)	Improved Initiative(B), Weapon Finesse(B)	Improved Initiative(B), Weapon Finesse(B)
Environment	Any	Any	Any
Organization	Any	Any	Any
Challenge Rating	2	1	1
Treasure	None	None	None
Alignment	Always Neutral Evil	Always Neutral Evil	Always Neutral Evil
Advancement	None	None	1/3 HD (Tiny)
Level Adjustment	~	~	~

Open Spoiler below for main stat block for Small through Large sinister spinal cords.

Spoiler

~	Sinister Spinal Cord, Small	Sinister Spinal Cord, Medium	Sinister Spinal Cord, Large
Size and Type	Small Undead	Medium Undead	Large Undead
Hit Dice	1d12 (6 hp)	2d12 (13 hp)	3d12 (19 hp)
Speed	20 ft. (4 squares), climb 20 ft., swim 20 ft.	20 ft. (4 squares), climb 20 ft., swim 20 ft.	20 ft. (4 squares), climb 20 ft., swim 20 ft.
Initiative	+7	+7	+7
AC	14 (+3 Dex, +1 size); touch 14; flat-footed 11	13 (+3 Dex); touch 13; flat-footed 10	12(+3 Dex, -1 size); touch 12; flat-footed 9
BAB	+0	+1	+1
Grapple	-6	+0	+5
Attack	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +3 Melee Touch)
Full Attack	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +3 Melee Touch)
Space/Reach	5 ft./5 ft.	5 ft./5 ft.	10 ft./5 ft.
Special Attacks	Paralysis, Strangle	Paralysis, Strangle	Paralysis, Strangle
Special Qualities	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits
Saves	Fort +0, Ref +3, Will +2	Fort +0, Ref +3, Will +3	Fort +1, Ref +4, Will +3
Abilities	Str 6, Dex 17, Con --, Int --, Wis 10, Cha 1	Str 8, Dex 17, Con --, Int --, Wis 10, Cha 1	Str 10, Dex 17, Con --, Int --, Wis 10, Cha 1
Skills	-	-	-
Feats	Improved Initiative(B), Weapon Finesse(B)	Improved Initiative(B), Weapon Finesse(B)	Improved Initiative(B), Weapon Finesse(B)
Environment	Any	Any	Any
Organization	Any	Any	Any
Challenge Rating	1/2	1	2
Treasure	None	None	None
Alignment	Always Neutral Evil	Always Neutral Evil	Always Neutral Evil
Advancement	None	None	4-5 HD (Large)
Level Adjustment	~	~	~

Open Spoiler below for main stat block for Huge through Colossal sinister spinal cords.

Spoiler

~	Sinister Spinal Cord, Huge	Sinister Spinal Cord, Gargantuan	Sinister Spinal Cord, Colossal
Size and Type	Huge Undead	Gargantuan Undead	Colossal Undead
Hit Dice	6d12 (39 hp)	12d12 (78 hp)	24d12 (156 hp)
Speed	20 ft. (4 squares), climb 20 ft., swim 20 ft.	20 ft. (4 squares), climb 20 ft., swim 20 ft.	30 ft. (6 squares), climb 30 ft., swim 30 ft.
Initiative	+7	+6	+6
AC	11 (+3 Dex, -2 size); touch 11; flat-footed 8	8 (+2 Dex, -4 size); touch 8; flat-footed 8	4 (+2 Dex, -8 size); touch 4; flat-footed 4
BAB	+3	+6	+12
Grapple	+14	+24	+37
Attack	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +8 Melee Touch)	(Paralysis Attempt +13 Melee Touch)
Full Attack	(Paralysis Attempt +4 Melee Touch)	(Paralysis Attempt +8 Melee Touch)	(Paralysis Attempt +13 Melee Touch)
Space/Reach	15 ft./10 ft.	20 ft./15 ft.	30 ft./20 ft.
Special Attacks	Paralysis, Strangle	Paralysis, Strangle	Paralysis, Strangle
Special Qualities	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits	Soft, Dark Vision 60 ft., Halt Immunity, Undead Traits
Saves	Fort +2, Ref +5, Will +5	Fort +4, Ref +6, Will +8	Fort +8, Ref +10, Will +14
Abilities	Str 16, Dex 17, Con --, Int --, Wis 10, Cha 1	Str 22, Dex 15, Con --, Int --, Wis 10, Cha 1	Str 28, Dex 15, Con --, Int --, Wis 10, Cha 1
Skills	-	-	-
Feats	Improved Initiative(B)	Improved Initiative(B)	Improved Initiative(B)
Environment	Any	Any	Any
Organization	Any	Any	Any
Challenge Rating	5	7	10
Treasure	None	None	None
Alignment	Always Neutral Evil	Always Neutral Evil	Always Neutral Evil
Advancement	7-11 HD (Huge)	13-23 HD (Gargantuan)	25+ HD (Colossal)
Level Adjustment	You are...	...kidding...	...right?

A grayish rope-like... THING is before you, tapering towards the back.

Sinister spinal cords are the spinal cords of corpses reanimated through a variant of the same necromancy that can create a skeleton or zombie. (See "Creation" below)

Combat
Because of their utter lack of intelligence, the instructions given to a newly created sinsiter spinal cord must be very simple. They generally end up simply charging enemies and then starting in with strangling once all opponents are downed (and continuing even if some of them recover).

Soft(Ex): An unarmed slithering spinal cord is utterly incapable of causing hitpoint damage per se (dropping hit-points due to lack of air are another matter entirely). It could be ordered to trigger a trap, or pick up a weapon in one end (but even then it would be non-proficient with it), but its only native attack that involves an attack roll is its paralysis touch. Armed or not, a slithering spinal cord is too clumsy with weapons to perform a coup-de-grace.

Paralysis(Sn): See table below for Durations and Will save DCs (Which are Consitution based and receive a +5 racial bonus), unlike most paralysis effects, the victim goes limp instead of stiffening up. This usually results in falling prone.

Strangle(Ex): If a sinister spinal cord grapples a helpless victim (which means they automatically succeed on the grapple check) no more than one size category larger than them the victim must save against its Paralysis, and must attempt a fortitude save to be able to breath that round. They receive a bonus (or penalty) to their save equal to there strength modifier, but a natural 20 is not an automatic success. Use the standard rules for holding the breath/drowning (in other words it will be many rounds before the victim is in any danger in most cases). The DC is unusual and is the sinister spinal cords strength SCORE + 1/2 HD + 5 Racial Bonus. A success reduces the effective count of rounds without breath by 1 (instead of increasing it by 1), while a success by 10 points or more allows a full breath or two, resetting the count to zero.

Note that while regaining the ability to move ends this effect, it does NOT end the grapple, which continues, although the victim does not count as grappled on any round they do not attempt to perform a grappling action against the sinister spinal cord still wrapped around their neck. The sinister spinal cord automatically succeeds with all touch attacks without the need for a roll against a creature it it wrapped around the neck of (saving throws against the paralysis are, of course, allowed).

Sinister spinal cords wrapped around necks count as flat footed to attacks if the following conditions are met:

1. Said attack are made with daggers, scalpels, scissors (which do not count as improvised weapons in this case), and similar bladed weapons and tools.
2. The attacker must be able to see the sinister spinal cord, which does NOT generally include the person whose neck they are wrapped around unless a mirror is used in which case a flat -1 to hit against the flat-footed sinister spinal cord is imposed.

Halt Immunity(Sn): Sinister spinal cords are immune to Halt Undead and similar spells and effects. Note that this specifically does NOT include rebuking (nor turning) nor purely mechanical effects such as Web, or Tangle-foot bags.


Auxiliary Table:

Size	Paralysis DC	Paralysis Duration	Strangle DC	Size of Source Creature
Fine	15	1 Round	6	Tiny biped*, Diminutive Other
Diminutive	15	1d3 Rounds	7	Small biped*, Tiny Other
Tiny	15	1d4 Rounds	9	Medium Biped*, Small Other
Small	15	1d6 Rounds	11	Large Biped*, Medium Other
Medium	16	1d8 Rounds	14	Huge Biped*, Large Other
Large(3 HD)	16	1d10 Rounds	16	Gargantuan Biped*, Huge Other
Large(4 HD)	17	1d10 Rounds	17	Gargantuan w/ 2 EHD Biped*, Huge w/ 2 EHD Other
Large(5 HD)	17	1d10 Rounds	17	Gargantuan w/ 4 EHD Biped*, Huge w/ 4 EHD Other
Huge(6 HD)	18	2d6 Rounds	24	Colossal Biped*, Gargantuan Other
Huge(7 HD)	18	2d6 Rounds	24	Colossal w/ 2 EHD Biped*, Gargantuan w/ 2 EHD Other
Huge(8 HD)	19	2d6 Rounds	25	Colossal w/ 4 EHD Biped*, Gargantuan w/ 4 EHD Other
Huge(9 HD)	19	2d6 Rounds	25	Colossal w/ 6 EHD Biped*, Gargantuan w/ 6 EHD Other
Huge(10 HD)	20	2d6 Rounds	26	Colossal w/ 8 EHD Biped*, Gargantuan w/ 8 EHD Other
Huge(11 HD)	20	2d6 Rounds	26	Colossal w/ 8 EHD Biped*, Gargantuan w/ 8 EHD Other
Gargantuan(12 HD)	21	3d6 Rounds	33	Colossal+ Biped*, Colossal Other
Gargantuan(13 HD)	21	3d6 Rounds	33	Colossal+ Biped*, Colossal Other
Gargantuan(14 HD)	22	3d6 Rounds	34	Colossal+ Biped*, Colossal Other
Gargantuan(15 HD)	22	3d6 Rounds	34	Colossal+ Biped*, Colossal Other
Gargantuan(16 HD)	23	3d6 Rounds	35	Colossal+ Biped*, Colossal Other
Gargantuan(17 HD)	23	3d6 Rounds	35	Colossal+ Biped*, Colossal Other
Gargantuan(18 HD)	24	3d6 Rounds	36	Colossal+ Biped*, Colossal Other
Gargantuan(19 HD)	24	3d6 Rounds	36	Colossal+ Biped*, Colossal Other
Gargantuan(20 HD)	25	3d6 Rounds	37	Colossal+ Biped*, Colossal Other
Gargantuan(21 HD)	25	3d6 Rounds	37	Colossal+ Biped*, Colossal Other
Gargantuan(22 HD)	26	3d6 Rounds	38	Colossal+ Biped*, Colossal Other
Gargantuan(23 HD)	26	3d6 Rounds	38	Colossal+ Biped*, Colossal Other
Colossal(24 HD)	27	5d6 rounds	45	Colossal+ Non-Biped or Large-Tailed Biped

*Not counting bipeds with significant tails such as Lizard-folk, Mepholk, etc.

Special: Sinsiter spinal cords are occasionally placed in the nasal passages of the creatures from which they came. In such a case the larger undead becomes somewhat subject to critical hits, sneak attack, and other precision based damage provided that they are dealt in the form of piercing damage. In such a case a confirmed critical hit may be elected by the attacker to deal its NORMAL (NOT critical hit/Sneak Attack!) damage to the sinister spinal cords instead of dealing any damage what-so-ever to the larger undead.

Usage: Best when mixed with almost anything that can coup de grace. Generally they will be deployed in front of or riding on the shoulders of ground troops.
Creating a Sinister Spinal Cord
First the spinal cords of of one or more creatures must be harvested, each one requiring a Heal check with a DC of 25. The spinal cords must be reasonably undecayed and whole and the creature must have had a spinal cord. Then Hold Person (for Large or smaller sinister spinal cords) or Hold Monster (for Huge or larger sinister spinal cords) must be cast once over each spinal cord of Huge or smaller size to be animated. For gargantuan and colossal sinister spinal cords Hold Monster must instead be cast once per 2 HD. Finally, either Animate Dead or Create Undead, Lesser must be cast. The spinal cords must each be wrapped around their individual material components for the spell. Each such casting (regardless of which spell is used) may create up to 2 HD worth of sinister spinal cords per caster level (The Desecrate spell doubles this limit). Animate Dead can not create a sinister spinal cord of over 20 HD. The size of the sinister spinal cord is two size classes smaller than the size of the creature for bipeds lacking tails that reach at least to their knees (or ankles in the case of digitigrade or unguiligrade species) the spinal cord was were taken from (to a minimum Fine Size), for almost all other species the sinister spinal cord is one size class smaller (again, to a minimum of fine). Sinister spinal cords have hit dice equal to the minimum listed for a pair of sinister spinal cords of that size, plus extra hit dice equal to 1/2 the number of extra hit dice above the minimum that the creature it was harvested from needed to achieve its size class (up to the maximum listed HD a sinister spinal cord of the particular size catagory it is at may be advanced to).
The remaining corpse is still suitable for animation into most types of undead. Especially note that with the right skill checks, spells, etc it is possible to generate a Skeleton, Slithering Liver, Zooming Brain, a contribution to a Fat Glob, 2 Rolling Eyeballs, a pair of Floating Lungs (which is a single creature), a Hopping Stomach, a Gut Snake, an Empty Skin, and a Dark Heart from a single corpse.




There are even rumors of a few rare individuals (mostly undead) wielding them in the fashion of whips or spiked chains (they deal no damage if wielded in this fashion, but if released upon a successful hit the gut snake may start a grapple as if it had made its touch attack). The size of sinister spinal cord that could be wielded in this manner would be the same size class than the wielder if wielded as a spiked chain, or one size class smaller if wielded as a whip. Even in this case the attack causes no hit-point damage.


Design notes:
As is usually the case the CR's are pretty much just guesses.
Combination of low attack bonus touch attack, will save, and fortitude saves means that very few characters will be weak against all the steps needed for one of these to kill on its own. This makes TPKs much less likely if they are encountered without any other sort of allied creatures. And given their nature, kills of an individual PC, with the rest of the party surviving, are even less likely.
EDIT: Forgot to mention that, from the beginning, the ability scores, movement rates, and hit-dice were based on Vipers, perhaps with a few minor changes, and, of course, extrapolated for the largest and smallest size classes.