Advice for facing CSM: Slaanesh

I am looking for any help you evil Archons and hermonculi can lend me in utterly destroying our nemesis Slaanesh.

I will be facing a pal of mine in a 1500 point game using my Dark Eldar vs his Slaanesh Chaos Space Marines. This is my first time facing Slaanesh.

Background of my opponent:

He will only be taking 1 helldrake, as he only owns one. He's fond of his 5 terminators and a defiler. the rest should be a mix of slannesh marines and cultists, possibly a winged daemon prince or Lucius the eternal as I have seen him use before.

My concerns:

I am of course worried about his ability to ignore cover and by extension my jink saves with his bolters, helldrakes, and blastmaster weapons. Also his 5 initiative models. Lucius the eternal looks almost designed to crush my archon in a challenge, i get hurt for hitting him and he gets better the more skilled i am...not a fun fight.

My plan

I usually run a heavy combat army, but i was thinking of taking some eldar allies and shooting him at max range with ravagers, a fire prism, aegis line/quad gun, ect.

My questions

Should I stay at range and avoid combat or man up and charge right in? If shooting, will Eldar help my shooting ability or should i not Allie?

Thank you for your help! Ill post a list i was thinking of using below.

Dark elder with eldar allies vs chaos
HQ-
Archon w/ husk blade shadow field

ELITES-
4 incubi  w/ klaivex, blood stone  
in a Venom w/ extra cannon

TROOPS-
5 wyches w/ haywire grenades
in a venom  w/ extra cannon

10 kabalite warriors  w/ dark lance
behind a ageis defence line  w/ gaud gun
   
HEAVY SUPPORT-
3 ravagers w/ 3 flicker fields

Eldar allies-
HQ-

spirit seer

TROOPS-
10 dire avengers  w/ exarch w/ p.wep shimmershield
in wave serpent  w/ twin linked scatter laser

Heavy Support-
Fire Prism w/ holo fields

I can't give much list building advice because I am rather new to DE and rather bad at them as well, but I am rather knowledgeable on CSM, as they are my other army.

First things first, your list.

1) Your worried about noise marines, and rightfully so. However a little known fact is that Noise Marines are sinfully expensive. Even with only modest upgrades a ten man unit runs at 250pts ish, which means they are rather vulnerable for that point value. Most importantly, blastmasters are surprisingly unreliable as anti-vehicle weapons in my experience, since you get very few shots and no re-rolls. If you can bracket them with high density shots or high ap melee they will fold fast, and he can hardly afford the casualties. Your incubi and venom's are your solution here.

2) Defilers are dead weight. They are very fragile for a 200+ unit. Target it with some Dark Lances and it will explode.

3) Lucious is overrated. He is great at wiping out massed crappy infantry, but your Archon will kill him before he can strike. No Eternal Warrior and only a 5++ is not his friend.

4) Chaos Terminators are shootier but generally less versatile in melee than their loyalists versions. If he is decked out with Power Sword/Lightning Claws, avoid melee except with incubi.

As for your lists,

1) You don't need 3 Ravagers, since you also have the Fire Prism, Quad Gun and Wave Serpent. Your friend is not even running a lot of vehicles, so that is plenty of anti-vehicle. Not sure where to spend the points, but I would recommend...

2) Spirit Seer is good, but you are probably better served with a basic farseer since you are not running Wraith units. Extra mastery level + better leadership/gear = win.

3) Upgrade the Wave Serpent's TL Catapults to a shuriken cannon. Like a Venom's Splinter Cannon, it's always worth it.

Hope this helps!

The Heldrake is by far and away the scariest thing in that list. Used in conjunction with the Noise Marines it will wipe your stuff out with terrifying ease, as they pop your transports and it torches the passengers. If he's careful with it he'll be able to avoid the quad gun, and even if he's not your chances of downing it before it does any damage are slim. The Noise Marines can be avoided through pre-measuring, and like Gorlan says the Blastmaster is pretty unreliable for AV - those little blast templates just slide right off Raider hulls if you have them facing them head on. Careful charging them or Lucius though - Doom Sirens will absolutely murder your Incubi.

I'd worry that you might be too heavy on anti vehicle fire when you could really do with more anti infantry. I wouldn't necessarily get rid of the Ravagers altogether, but at least one, maybe two, could be equipped with Disintegrator cannons. If it's a friendly game, I'm sure your friend won't mind you proxying them if you have them assembled with lances (although he might feel differently about this when they draw a bead on his beloved Terminators!)

Those 5 wyches won't make it to a vehicle unless they're extremely lucky, as presumably the Defiler will be sat at the back, with half a Chaos rabble between you and it. Five Warriors with a blaster might be a better investment, as they're slightly more survivable in a firefight, as well as bringing more anti-infantry shooting to the table. If you're intending charging transport vehicles (if your friend has any) with the wyches, there won't be enough of them to surround the exits, and they'll get shot to bits next turn even if they do wreck it.

Any points you can save should be spent on Holofields for the Wave Serpent too. Keep it moving fast enough and it will be a royal pain fr him, with a 3+ cover save after moving flat out as well as the Serpent Shield. Once enough of the stuff that can penetrate armour 12 has gone, fire the shield at those cowering cultists!

I understand the reasoning behind taking the Spiritseer, as it's the cheapest HQ. The ability to give shrouded to the unit behind the Aegis, giving them a 2+ cover save without having to go to ground, is very useful too. Anything else he rolls can only help you too.

All in all, try and cripple or slow down as wide a range of stuff as you can before the Heldrake shows up. Fire the dark lances at any transports BEFORE the Fire Prism, you'll be kicking yourself if you crack it open with the Prism Cannon then don't have a lovely AP3 pie plate to put on the occupants! Don't fire the focussed shot at the Terminators unless there's no more power armoured stuff left to shoot at or if they're coming for the Fire Prism itself. It will scatter, it's so certain as to be almost written in stone...

Lots of dissies and a Void-Raven Bomber! People are surprised how many fliers my V-Bomber shoots down. Oh and lots of venom might help. For allies, I would run maybe a fire prism, a Farseer w/ 5 Wraith Gaurd in a Wave Serpent, and Gaurdians with an Aegis. I think the Gaurdian weapon platform has some sweet skyfire thing with Str. 8 too I believe.

Some excellent advice, gorlan, Mr believer and eganize,

I usually love my wyches with grenades in a venom but ya there be useless in this fight so blaster kiting it is.

I think i will drop a ravager and instead take more troops for objective nabbing, and to try and out number his smaller forces.

Well the battle went well, i tabled him by the end of turn 3 when his cultist blob fled from my archon and I ran them down. with my 6 victory points to his zero I can honestly say I had no reason to be worried.

The mvp of the battle was the aegis quad gun, it dealt the final blow to his defiler and killed heldrake.

Im thinking I should try and make a dark eldar themed aegis defence line of slaves chained up on their knees. A mix of all the races showing dark eldars dominance over them

That would be a really sweet Aegis Line! Also 'grats on your victory.

Yea helldrakes are your biggest concern, they will turn our army too ash unless you have a solid air defense. Also a spirit seer makes wraithguard troops and they will then benefit from fearless and can dish out terrible damage too enemy vehicles. I also am in love with the wraith knigtht standard. He won't worry about much of their fire and will wreck havoc in their backfield by turn 2