I'll preface this with the oh so common, I have been out of the hobby (playing that is) for nearly 6 years. Thus I have no clue how anything actually works. That being said, this is what I've come up with thus far.
Battalion Nurgle Daemons
Great Unclean One with Doomsday Bell and Bile Blade, Fleshy Abundance and Miasma of Pestilence - 250
Great Unclean One with Doomsday Bell and Bile Blade, Virulent Blessing and Fleshy Abundance- 250
Horticulous Slimex - 150
3x 3 Nurgling bases - 54 - 162
Battalion Alpha Legion
Master of Possession, Infernal Power and Cursed Earth - 88
Master of Possession, Mutated Invigoration and Sacrifice - 88
3x 10 Cultists with Auto Guns - 40 - 120
3x 3 Oblits - 285 - 855
Basically this is just a brick that you throw at your opponent and see what happens.
The first thing I like about this is the redundancy that is obvious in this list. Which is my favorite tactic because it forces your opponent to over-analyze their moves, increasing their chances of making a wrong one. This is doubled by the amount of target saturation that is built-in. Do you shoot at the oblits or the GUO? You have to take both GUO out in order to have this list start to fall apart.
The rules that I'm trying to take advantage of is the Doombells, which allow you to bring back a model from a Nurgle Daemon unit on a 4+ each turn. This applies to both the Oblits and Nurglings, which is why there are two GUO in the list, in case one goes down, I still have one to use this.
Secondly, the abilities of the GUO to heal up to 2D3 wounds a turn helps (1 from the strat and 1 from the power). Furthermore, the Sacrifice power allows me to heal and bring back Obilts as well.
On top of getting any wounds to stick, there is the matter of getting the wounds in the first place.
Obviously the AL trait offers the -1 to hit for the oblits, MoP and Cultists. Then you have Slimex, who drops a Gnarltree thing each time he moves, which gives your Oblits a +2 cover save to their 2+ anyway. Once you also cast Cursed Earth, they all boost to a 4+ invul save with, effectively a 0+ cover save beforehand, making weapons with a -2 AP pretty much obsolete.
The other powers to mention are Infernal power, to let your oblits re-roll 1's to hit AND wound. Mutated Invigoration to hopefully boost one of the Oblits shooting (whichever has 3 standing really). And with all of this is the Nurgle Loci that makes all wound rolls of 6+ for Nurgle Daemons score an extra damage. Obviously you can see the benefit there.
This is a very slow-moving army, however, the AL strats allow you to redeploy units mid game, or late game. Which should help to grab objectives (if they are as big in 9th as in 8th).
The biggest issues or difficulties I'm having is what Warlord Traits and Artefacts to pick. I know I want the Hydra's wail and probably the Drakscaleplate.
Let me know what you think. I am just going to build it to have fun and piss people off (in a joking/annoying way, not intentionally trying to hurt feeling here, which it's Nurgle so it can't lol).
All comments are appreciated