This is a neat build. At first I was turned off by the redundancy of the creatures overlapping with Atheros ability. I figured ETB/LTB effects would be the best way to abuse Atheros. But I am sucker for gimmicks/themes and I like the direction of this.

Bloodghast and Nether Traitor are auto includes to this strategy.

PlagueSpitter would be an upgrade to Noxious Field.

Deathgreeter, Cruel Celebrant, Daxos, Blessed by the Sun, Harvester of Souls, Body Launderer, Pitiless Plunderer, etc. type effects might be the engine missing from this strategy.

Vanishing Verse is slowly becoming one of my favorite removal spells. It would round out the playset of Orzhov exile.

Crypt of Agadeem on theme land.

And as always Null Brooch = <3

Ok. I guess Null Brooch is my one true pet card above them all. It fits anywhere haha! Let's see. First, I didn't add Bloodghast because it can't block. I definitely need to add in Nether Traitor. I wasn't sure whether I should add cards like Plague Spitter or not because they are creatures and they could die (unless I get Avacyn out fast). This is why I chose Noxious Field instead. It will stay around along with Death Pits of Rath even when all creatures are dead on the board and I will still have a way to kill all creatures every turn. I definitely want to add Harvester of Souls and Pitiless Plunderer. They synergize beautifully with this deck. Creatures that gain me life or make others lose life for creatures dying isn't something I'm sure I want to add. I will need to test what I have more before I decide. I don't think Body Launderer will be the best for this deck. I'm not sure I would add it. Vanishing Verse isn't really necessary. I have WAY more than enough removal as it is. I can try and squeeze in Crypt of Agadeem but I don't know if it will get much value. I'm going to add Citanul Flute in here as well. I mainly chose Athreos, God of Passage as the commander just to make my creatures come out even faster unless someone wanted to pay the life. Hopefully I will finish updating this today and run some tests. Thank you SufferFromEDHD for all of your suggestions and help. I really appreciate it!

I told you on one of your other decks the way you utilize Null Brooch is how I also approach deck building. It really does fit anywhere! (except in mono blue decks)

How do you feel about Imp's Mischief and/or Rebuff the Wicked?

Martyr's Cause solid engine similar to Gate to Phyrexia.

Citanul Flute is that old school janky tech I love seeing being used to it's full potential.

I suggested Plague Spitter because it is the creature version of Noxious Field/Pestilence. After looking thru your creatures again I see a very clear theme that it does not fit into. Still a cool card that has synergy with the strategy and abuse potential alongside Athreos.

I've updated the deck again. I would like to add Martyr's Cause, Harvester of Souls, Pitiless Plunderer, and perhaps Anowon, the Ruin Sage and Chainer, Dementia Master. Suggestions on what to cut? I don't think I will add Imp's Mischief or Rebuff the Wicked. Not sure what I would cut for it. Removal perhaps? All of the scary spells that I would mostly worry about aren't targeted. Also, I may want to add more sacrifice outlets. Not sure what else I would add though.