Sooo we had the match. I lost but not as badly as i expected. A quick Summary/rundown:
First, the lists.
Daemons
Herald of Tzeentch on a chariot jetbike thing with Bolt and gaze
2*5 Horrors
1*4Flamers
3*9 Screamers.
He also mentioned he will never be fielding this list ever again. Hooray!
CSM
Nurgle Lord on Palaquin with Black mace and Burning Brand
20 CSM with 2 Flamers, extra CCWs (keeping their Bolters) MoS and Icon of excess. <---This unit is the only real tailoring I did for the list after listening to you guys.
20 Cultists
7 Plague marrines with 2 Melta <--Lord here
5 Raptors with 2 Meltas, Combi melta and Gift (These two units are copy pasted from a different list as I really like them normally.)
Warlor traits had 0 effect on the game.
Mission was the relic one.
For the first 2 turns, nthing happened. I moved up and ran towards the relic. 2 units of screamers, the herald and 1 unit of Horrors came down Turn 1. (The horrors fell off the table. First blood to me!) Turn 2 saw the other Horrors come down. Everything hid out of, either range, or line of sight.
Turn three saw me grab the relic with my cultists, pass it back a guy and drop it an inch to get it out of the lava we accidnetly placed slap bang in the middle of the board. (Incidently that lava was aparrantley some flavour of red jelly as no-one was singed by it all game.) His final Screamers come down along with his flamers, causing his other Screamers to come out of hiding. But my Slannesh Marines being completely surrounded by a barrier of the other units must have made him a little scared as no charges were called, instead he turboboosted after flaming a cultist and a couple of Plague Marines(being just out of range for any real damage)
Turn Four was where the real battle begun. My Cultist ran through the lava forming a much sturdier barrier between my Marines and the Screamers. The Plagues took the rear right to protect from the third screamers and took some shots at the Flamers to try and whittle them down before they can cause any real damage with their flames. I kill 1. All other shooting (including the S5 Combi Bolter of my Gifted Rapto Champ

) knocks 1 unit of Screamers down to 3 Mantas. The relic is now in the hands of a Slanneshi man.
Flames kill about four(I think?) Slannesh Men and Two Plagues. FNP is my friend. The three man screamers declare against my Plague, soaking up the over watch before a nine man Screamers charges as well. (The three man actually failed their charge as well) The other Nine Manta unit charges the cultists.
Assault sees My Lord Hit himself in the face with his Mace but still manages a wound (The ensuing Toughness tests kill 2 mantas) before the sheer amount of Str5 Ap2 attacks melts the unit all at once. The cultists meanwhile never stood a chance.
Turn Five: The Slanneshi Marines bring the pain, Flaming and Pistol shots taking revenge on the cultist killing Mantas reducing them to just three left. They then charge and cause enough wounds to kill 4.5 wound worth of Mantas wiping 1 off the board, just 2 to go. The Raptors attempt to wall off my scoring Slanneshis but fail.
Flamers do what they do before declaring a charge to soak up Overwatch. The Seven man and three Mantas charge too. I kill 2 Mantas before exploding horribley.
Turn Six. My only remaining unit, the three man Raptors, (having taken glanceing hits from the Flamers earlier) go for the moral vic tory and retreat towards my board edge but fail to make it. They are then burned alive by Flamers. I'm Tabled.
The Relic had been my only hope for a win. Combined with my already taking first blood earlier(Deep strike mishap) and his mistake of keeping his horrors out of the battle meant his only chance was to kill me to a man, and he succeeded. My hatred for Screamers grows as my brain wracks itself for a unit that could reliably counter the buggers.
The only unit that comes to mind is allying in 30 Orks with the Mad Doc for a horde of unfeeling Orks, or fight fire with fire and ally in some Screamers of my own...(NO NEVER I REFUSE)... or Maybe a Great Unclean One... interesting.
Edit: Also I should probably add that while being the hardest fight I ever been to, it was actually a lot of fun. I do want revenge though. Tzeentch, why!! You were my fave God! Now Khorne and Nurgle will fight for your place.
And Slannesh too I guess...