The Wraith Gate
As an Eldar player who regularly plays with Spiders, I thought it would be good to add some of my own insight for perusal. I am not knocking CoolKidRoc or Fritz, as I understand neither play Spiders regularly.
The Warp Spider Aspect Warriors
From the second edition codex: The Warp Spiders are heavily armored and use a compact warp-generator to leap short distances through the warp. Their favored method of attack is to warp within a short distance of their foe and discharge their Death Spinner mon-filament guns. these weapons are deadly, but have a relatively short range, and are therefore well suited to the Warp Spider' special abilities.
Warp Spiders are jump troops from the Fast Attack slot. As such, they have a 12 inch move and can always deep strike unless specifically prohibited by the mission.
Spiders are also one of the few units we Eldar have that come with a 3+ save. This is nice, but the "heavy armor" robs them of the typical Eldar Fleet ability.
Losing fleet is not really a down-fall, as Spiders are clearly an aspect that focuses on shooting. Each spider comes standard with a Assault 2 Str 6 AP - weapon. That's correct, no ap on their weapon. This means that everyone will get saves against their shots, and you take a -1 to damage on the vehicle chart. Then again, look at the fact this is 2 shots at Str 6, on a unit that has base BS of 4. Typically your putting out 1 wound per model per turn, with a slight upswing to 2 wounds more often than not.
Lastly, the Warp Jump Generator (jump pack) gives the Spiders an interesting little twist of an ability. During the Assault phase, Spiders who are not assaulting or locked in combat can pick a direction and "jump" up to 2d6 inches in that direction. This lets them replicate the Jump-Shoot-Jump tactic that Tau use to great benefit.
The Warp Spider Exarch
From the 4th edition codex: The Warp Spider Aspect Warriors epitomize this doctrine of aggressive defense. Using a compact warp-generator housed within their armored backpack, they can make short warp-jumps, disappearing and reappearing in the blink of an eye. This enables them to make totally unexpected attacks on their foes, though it does necessitate spending a short time in the Warp. For this reason the Warp Spiders are considered the bravest of all Aspects - they risk not only their lives in the name of victory, but also their souls.
As all Exarchs, the Warp Spider Exarch functions as a "force multiplier" for the squad, enabling access to wargear and activating Exarch Powers. The Exarch shares the same armor save and leadership, but raises WS and BS to 5, Initiative to 6, and Attacks to 2.
In the realm of Wargear, there are 3 profiles that are typically available to equip your Exarch. First is leaving the Exarch matching the squad with a Death Spinner. This makes no sense.... don't do it.
Next you can equip your Exarch with a Spinneret Rifle. This equipment option is one that you will need to do some custom modification/scratch building for your model to accomplish, as there is no physical bit option for your model. The Spinneret Rifle adds an 18" shot to the unit thats AP 1 and pinning. Interesting but not what I have played (or commonly see played).
Lastly you have the wargear option that is typically seen on the table. This is partially due to its how the current Exarch model is sold. I also believe this is the most effective option. You can equip your Exarch with Dual Death Spinners (makes his standard gun Assault 4) and Powerblades (adding +1 attack and turning attacks to power weapon attacks).
From a power standpoint, Exarchs have two choices:
Surprise Assault: This allows the squad to always deep strike even when prohibited
Withdraw: Gives the squad Hit & Run
If your going to give your Exarch a power (I do ~25% of the time), I recommend going with Withdraw. Surprise Assault is pretty much wasted points and there are better places to spend the points.
What do I do with them?
So that's the question, "How the hell do I use this squad?"
Let me try and answer your question with a simple answer first:
What? You mean I am going to throw out a 10 man squad costing ~247 points into the middle of the field? Surely he did not mean aggressively. He must have meant cautiously forward or some crap like that.
No.... simply put I said use them Aggressively!
Ok, listen up neophyte Autarchs. This is an aspect that can fully live up to its fluff and does so in a fantastic way. They are courageous. They attack unexpectedly. They get in close, unleash mono-filament deathie hell and then blink away! Yeah, I said deathie.
I know that others (many others) will tell you that Spiders are not worth it. They just do not work well. To quote CoolKidRoc: "Wow was I surprised at how well these guys perform."
When used aggressively these guys will mess up your opponents plans, knock out some light transports, force-disembark their troops, and shift your opponents attention away from your main force. In addition, it will regularly force your opponent to focus on their back-field and start reacting instead of on their front-field. Whats that you say? These are all the things great 40K tacticians urge us to do? You are correct.
I get the best use from my spiders by deep striking them aggressively into my opponents battle lines, often behind or to the side of some transports or tanks I want to pop. I take risks with my deep strikes, with the experience that when things do not go horribly wrong, spiders in the back-field are a very scary proposition for my opponent. Now, there will be times when they mishap and do not just go back in the warp. They will mishap and decide to stay in the warp and camp out all game. Yup, this sucks. Then again, the rest of the time (when they do not mishap and die) they contribute beyond their points to my side of the game.
In addition, in that other circumstance where they mishap and your opponent places them... well that really does not suck too badly. These guys have a 12 inch move, a d6 run, and a 2d6 assault jump. It does not take long to get them back into the fight.
Yes, I am aware that Autarchs are not Spiders. Ocassionally our brother Autarchs pass through the path of the Spider on thier way to our august ranks on the council. These intrepid brothers often keep their personal Warp Jump Generators (WJG) around for that odd occasion when they can join the Spider Aspect Warriors in the field.
So let's take a bit to discuss the added benefit an Autarch can bring to our Spider squad. The DTP regularly bring an Autarch to battle who can join the spider squad. This brings an additional power weapon to the squad in the rare occurrence they are charged. More important, this brings a fusion gun to the squad, which adds a melta shot at short range and a str 8 ap 1 shot at the same range as the spiders. This increases the threat the Spiders bring with them along with providing a +1 option to reserve rolls.
Suffice it to say I recommend the use of Spiders in most Eldar armies.The only true downside I see to them is thier actual model. The models need to be updated, as they are clearly dated and are not great looking models.
How do I run mine? I run my spider squad in groups of 7 or 8 (depending on room in the list) plus an Exarch equipped with Power blades and dual spinners. When running this squad I also have an Autarch join them, equipped with Mandiblasters, power weapon, fusion gun, and WJG.
This squad is large enough to inflict damage to both hoard armies along with elite armies. It can crack light vehicles, which are everywhere in 5th, and threaten the troops that pop out. They also interrupt my opponents plans and cause havoc in their back field.