So the idea is to build an early board position through small creatures with come into play abilities. I want to try and attack early and often in order to get the most out of Athreos later in the game. I have found that if I can play 1 or 2 creatures before turn 3, then cast my general on turn 3, it puts a ton of pressure on my opponents. One downside is if my general gets "tucked" my deck basically rolls over and dies. I would like to add more tutor effects and sacrifice effects.

General : Athreos, God of Passage

Creatures: (in order of CMM least to greatest)
Kami of False Hope
Viscera Seer
Vigilant Martyr
Grand Abolisher
Cartel Aristocrat
Tidehollow Sculler
Leonin Relic-Warder
Augur of Skulls
Nezumi Bone-Reader
Knight of the White Orchid
Vampire Hexmage
Ravenous Rats
Black Cat
Brimaz, King of Oreskos
Offalsnout
Fiend Hunter
Blade Splicer
Mentor of the Meek
Necrotic Sliver
Sin Collector
Phyrexian Rager
Fleshbag Marauder
Bone Shredder
Disciple of Bolas
Sublime Archangel
Magus of the Disk
Disciple of Phenax
Ghost Council of Orzhova
Hell's Caretaker
Fleshwrither
Hero of Bladehold
Erebos, God of the Dead
Obzedat, Ghost Council
Divinity of Pride
Karmic Guide
Deathbringer Liege
Soul of Innistrad
Sun Titan
Treasury Thrull
Reveillark
Elesh Norn, Grand Cenobite
Sheoldred, Whispering One
Vish Kal, Blood Arbiter

Instant:
Path to Exile
Vampiric Tutor

Sorcery:
Demonic Tutor
Dread Return
Unburial Rites
Living Death
Army of the Damned
Debt to the Deathless

Artifact:
Sol Ring
Orzhov Signet
Armillary Sphere
Mortarpod
Mind Stone
Spear of Heliod
Godsend
Phyrexian Reclamation
Phyrexian Arena
Infernal Tribute
Attrition

Land:
12 Swamp
10 Plains
Esper Panorama
Evolving Wilds
Terramorphic Expanse
Marsh Flats
Orzhov Basilica
Orzhov Guildgate
Godless Shrine
Command Tower
Fetid Heath
Temple of Silence
Isolated Chapel
Windbrisk Heights
Bojuka Bog
High Market
Vault of the Archangel

As you can tell from the list, I have a slight discard theme going. I generally try to get a key spell from my opponent in a key situation than to try and empty their hand.
I want to keep the average CMM as low as possible. I know cards like Black Cat are not what you see in a normal Commander game, but I found that with Athreos continually restocking my hand, I need to be able to keep a tight curve so I can keep recasting my spells.
I would appreciate any comments or suggestions from you.
Thanks for taking the time to look at my deck!

Faith Healer and Vigilant Martyr are in my Athreos deck. Both protect Athreos, and he protects them. Feel the <3!

Have you considered the bestow creatures? They don't have the ETB effects, but you can play them out as creatures early, sac them for value, return them (or bolt your opponent), and then bestow them, and then have sweeper insurance and more sac value if the first guy dies. Spiteful Returned, Baleful Eidolon and Hopeful Eidolon are cheap enough that it shouldn't mess with the curve and have decent abilities.

If your curve is super low, you may consider a few Extort creatures (other than the Treasury Thrull you're already running). The problem is only one has an ETB effect and it's kinda meh. Even so, at least Pontiff of Blight is worth considering, because if you have a small army that can't get through for some reason, that guy turns every creature you play into a big life swing. He could be an alternative closer; he certainly has to get answered somehow or else every turn is going to be a +18 life or something crazy.

Bloodchief Ascension would be a total nuisance for your opponents in that deck and can get you huge value from your commander since they just stop paying life.

Suture Priest could be good, though it lacks ETB value itself. Or Inquisitor Exarch if you something similar as ETB.

Otherwise, I've been looking forward to seeing this kind of treatment for that god, and this deck looks brutal. I approve.

with this two cards and a lot of demonds a gay here made a really good deck.

Thanks for the tips guys,
I've taken these cards out:
Keening Apparition
Gatekeeper of Malakir
Kor Cartographer
Captain of the Watch
Swiftfoot Boots
2 Swamp
2 Plains

Cards I've replaced them with:
Vigilant Martyr
Fleshbag Marauder
Bone Shredder
Soul of Innistrad
Vampiric Tutor
Windbrisk Heights
Marsh Flats
Isolated Chapel
Temple of Silence

I removed Keening Apparition because I only need 1 enchantment removal spell and I already had Leonin Relic-Warder. Gatekeeper of Malakir got cut because Fleshbag Marauder is an upgrade. Kor Cartographer got cut because I found that I would try to recast it every turn and it did little to advance my board or give me an advantage. I removed Captain of the Watch because it was the worst of my 6 drops. I cut Swiftfoot Boots because I don't care about my creatures dying and it doesn't contribute to my devotion.

Vigilant Martyr seems really sweet. It protects all of my creatures, and my general from removal. Bone Shredder is a good removal spell that I get to target with Sun Titan. I haven't had a chance to try out Soul of Innistrad, but with all my low CMC creatures, it seems like a sweet card. I put the Vampiric Tutor to help the deck become more consistent.

Vigilant Martyr is a sweet addition. Thanks so much for the advice!

The deck can get a roll easily and quickly drain your opponents. I kinda like the idea of Spiteful Returned as another way to drain them. The other bestow creatures just seem too meh to me.
I tried Pontiff of Blight for a while, but he would usually turn me into a big target without advancing my board. Also, in order to maximize his ability, you have to commit a ton of mana to each spell you cast. So instead of playing a bunch of spells in a turn and advancing your board state, you end up only casting 1 spell a turn.
What do you suggest I remove for Bloodchief Ascension. Again, it can be good, but it feels too cute.
I really like the idea of a Suture Priest in the deck to punish infinite token strategies.
I'm thinking that the weakest card in the deck right now is Godsend. I don't really have any "must block" types of creatures. So Godsend basically becomes a "pay 6, deal an additional 3 damage to target player" I'm going to try your suggestion of Suture Priest in place of Godsend tomorrow night.

Great list! A friend of mine has built an Athreos deck himself and I think I'll look at your list with him for some ideas. His is more centered at circling the creatures with Athreos, rather than attacking with them. What I would recommend from his list is:

Blood Artist - better than Suture Priest
Teysa, Orzhov Scion - so far, she works very well
Haunted Crossroads - we're still looking for a place for this one. It plays a terrible mind game on your opponents.
Butcher Ghoul - this one's deceptively strong. I'll just leave you to think about the interactions between Athreos and persist/undying for a while. Take your time
On the same note: Puppeteer Clique, Geralf's Messenger (triple B is a bummer, though) and maybe Cauldron Haze
I do NOT, however, encourage you to go all the way to including Dark Mike. That's just unfun.

And finally:
Ornithopter - I'm serious. Any zero-cost creature, really, but this one has flying, so it's a better chump-blocker. Just imagine: "Cast Ornithopter, sac it to Viscera Seer. You there, with 5 life remaining, do I get it back?"

Good luck with the deck!

Cavern of Souls is a good one if your play group runs a decent amount of Spell Crumple and Hinder. I know that I try to include it whenever my general is the keystone of a deck. Opal Palace might also be a decent inclusion. Since Athreos is 5 power it will shift him from a 5-hitter to a 4-hitter the first time and then a 3-hitter the second time; I figure you have so many cheap dudes he's probably a creature a fair portion of the time.