Help with a monster?

[Dyrynify]

Ok, folks, I am working on a monster, and finding myself stumped. I have never been all that great at building custom baddies, other then NPC's, so find myself needing help.

What I am aiming for: Fast and cunning, with powers that make them great ambush predators. I would like to get a CR 10 - 12 out of these things, if possible.

What I have so far:
Threath
Size/Type: Medium Magical Beast
Hit Dice: 8d10+8 (44)
Initiative: ?
Speed: 80 ft.
Armor Class: 15 (2 Dex, +3 natural)
Base Attack/Grapple: ?
Attack: Claw ?
Full Attack: 2 Claws
Space/Reach: 5 ft./5 ft.
Special Attacks: Greater Invisibility 1/day, Dimension Door 3/day
Special Qualities: Darkvision 60 ft., low-light vision, Scent
Saves: ?
Abilities: Str 21, Dex 14, Con 13, Int 5, Wis 16, Cha 14
Skills: ?
Feats: ?
Environment: Jungle
Organization: Solitary, Pack (3-6), Hive (20-40)
Challenge Rating: ?
Treasure: None
Alignment: Always neutral
Advancement: ?
Level Adjustment: -

So, lots of blanks there. What I need is help bringing these guys up to snuff, or ideas for monsters that fit this niche better.

[Tvtyrant]

At-will Invisibility and Silence SLAs, big bonuses on jump and climb and some sort of jumping pounce? It silences itself and makes itself invisible while it jumps from tree to tree, comes smashing down on the enemy from on top.

[Grayson01]

Use some of the Special ablilities, Skills and feats off the Displacer Beast that. Also have it take Improved Int or Improved Natural Attack. Spring Attack wouldn't be bad doubled with Trip or Pounce. Runs buy (wile Invisable) Trips the PC and keeps going so it can Attack of Oppertunity a defferent PC. Combat Refelxes might be a waste but not a bad idea. I see you only have 2 claw attacks will it also have a bite? As for the Claw/bite Size Imagine in your head what the creature looks like pick a Medum creater that is about the same size and use that as it's base Damage (then Bost it with Imporved Natural Attack). Since it has 8 hit dice it will have three feats so you can play with that a bit.

[Fyermind]

I would suggest increasing the HD to 10-12 if you want it to be a CR 10. Here I have written it with 10 HD. I have envisioned it as a fast shadowy hunter ensnaring it's foes in darkness and whenever possible using pack hunting tactics to incapacitate multiple foes and finish them off with sneak attack. Their weaknesses are fear effects, effects targeting their will saves, and damaging effects that are not subject to concealment. If you had a different idea for them, let me know and I can design them a different way.

Threath
Size/Type: Medium Magical Beast
Hit Dice: 10d10+10 (65)
Initiative: +6
Speed: 80 ft.
Armor Class: 15 (+2 Dex, +5 natural)
Base Attack/Grapple: +10/+15
Attack: Claw +15 melee (1d6+5 shadowy grasp)
Full Attack: 2 Claws +15/+15 melee (1d6+5 shadowy grasp)
Space/Reach: 5 ft./5 ft.
Special Attacks: SLAs: Dimension Door 3/day, Shadow Pounce, Shadowy Grasp, Shadow Constrict, Sneak Attack (4d6+10), Snuff the Lights
Special Qualities: Spell Resistance 20, Perfect Darkvision, low-light vision, Scent, Child of Shadow, Shadow Minions
Saves: +8 fortitude, +9 reflex, +6 will (-2 on will saves VS fear)
Abilities: Str 21, Dex 14, Con 13, Int 5, Wis 16, Cha 14
Feats: Track (racial bonus feat), Improved Initiative, Quicken Spell-like Ability (Dimension Door), Craven, Power Attack
Skills: Hide +16*, Jump +29, Move silently +17, Survival +7
Environment: Jungle
Organization: Solitary, Pack (3-6), Hive (20-40)
Challenge Rating: 10 ish
Treasure: None
Alignment: Always neutral
Advancement: add HD I guess. if you double it's HD make it large?
Level Adjustment: -


Shadow Pounce (Su): After being the target of a spell, spell-like ability, or effect of the teleportation subschool, a Threath can make a full attack against any target within reach.

Shadowy Grasp (Su): A threath may make a grapple check as a free action against any creature hit by it's claws. Success means that the target is now grappled in shadows. Creatures grappled in shadows cannot move from their space without escaping the grapple and is treated as blinded until it escapes the grapple.

Shadow Constrict (Su): Each round at the beginning of it's turn all creatures effected by the Shadowy Grasp ability of a threath must make a grapple check or take 1d6+2 Strength damage(1d6+the threath's charisma modifier).

Shadow Minions: Humanoids whose strength scores are reduced to 0 by Shadow Constrict raise a shadows under the Threaths control. A threath can control (Threath's HD * 2) HD worth of shadows at any given time. If it gains more shadows than that, it can choose which shadows leave it's control.

Child of Shadow: As long as a Threath travels at least 20' during it's turn (including via teleportation) it has total concealment due to shadows swarming around it. (this replaces the greater invisibility SLA)

Sneak Attack: +4d6 (+10 from craven) (An advanced Threath gains +1d6 sneak attack for every additional 3 magical beast HD it gains)

Perfect Darkvision: Threath's see normally in all shadows (magical or otherwise).

Snuff the lights: As a standard action a Threath can put out all mundane light sources within 30' and automatically suppress all magical light sources of level 3 or below within the area for 1d4 rounds. Supernatural light sources get a save DC 16 (the DC is charisma based) to resist being suppressed for 1d4 rounds.

Skills:
Threath's have a +8 racial bonus on hide checks this increases +20 racial bonus on hide checks while moving and in shadow natural.
Theaths have a +8 racial bonus on move silently checks, and a +4 racial bonus on jump checks. (note that the speed of a Threath gives it a +20 bonus on jump checks)
Due to it's excellent sense of smell Threath's have a +4 racial bonus on survival checks.

[Dyrynify]

I would suggest increasing the HD to 10-12 if you want it to be a CR 10. Here I have written it with 10 HD. I have envisioned it as a fast shadowy hunter ensnaring it's foes in darkness and whenever possible using pack hunting tactics to incapacitate multiple foes and finish them off with sneak attack. Their weaknesses are fear effects, effects targeting their will saves, and damaging effects that are not subject to concealment. If you had a different idea for them, let me know and I can design them a different way.

Forgot to mention this in the original post, but the impetus for these creatures was a sketch a friend did, which managed to combine a wolf and a praying mantis; the body was lupine, and the head was mantis, with a pare of mantis front legs/claws coming out of the shoulder. That is what I was thinking, but adding the shadow component is a nice touch.

[Fyermind]

Knowing that know I might have tried to put more of a jumping focus into them, but I'm not sure how I'd go about it. The thing with high CR opponents (generally speaking anything above CR 6) is that they need something special about them. All monsters really need something to set them apart, but at lower levels, that can be mostly fluff and maybe a feat or two. At higher levels that turns into having a set of special abilities that mesh well together in some unique ways. If they are supposed to be recurring villains they need substantially more cool tricks so that every fight with them isn't the same.

Threaths as I wrote them are not designed to be recurring villains. Every fight with them will look pretty much the same. They will full attack or snuff the lights, then quicken a dimension door to full attack somebody taking advantage of surprise and their shadow effects to get sneak attack. If anyone scares them or they start losing HP too fast, they Dimension door away and start running.

To make them interesting in more than one fight, either give them support, or have the surrounding environment be significantly different (the encounter will feel be much harder if there is no natural light, the addition of difficult terrain will make it easy for the threaths to escape if they need to). Of course, the PCs will likely face the same individuals more than once if they can't kill them in one shot, so don't be afraid to have the same set of threaths attack multiple times with the same tactics until the PCs figure out a way to stop them.

A DC 20 knowledge (nature?) check should be enough to identify them. A DC 25 check should reveal they use shadow effectively to weaken and trap their opponents. A DC 30 check should reveal they are skittish and weak of will.