This is a casual, Theros and Enchantment-themed, EDH deck. It's primary purpose isn't necessarily abusing Athreos' ability. That said, it is very helpful and can create some neat interactions in the deck.
The two most important things to remember are that this is 1.) CASUAL, 2.) MULTIPLAYER, and 3.) a THEMED deck. Because of this, it has quirky interactions that do useful things, but may include sub-optimal cards for the sake of matching the theme.
Of Note: This deck is built from cards I currently own. All suggestions are welcome, however.
Theme
The big thing is enchantments. Everything centers around them. There are 36 Enchantments in total, spread across base enchants, auras, artifacts, and creatures. Because the deck centers around a permanent type, it is also very easy to attain and keep devotion. Thus, Athreos becomes viable as a means to victory.
Most of the non-enchantment cards support the theme. Cards like Mesa Enchantress, Silent Sentinel, and Treasury Thrull help maximize the usefulness of your enchantments.
MEANS TO VICTORY
1.) Voltron!!!!!
The number of permanents in this deck leads to an easy time with Devotion (unless, of course, you are playing griefers [sad face]). My favorite thing to do is reach devotion with Athreos and then start enchanting him so that he can survive a board wipe and still remain a creature due to all the auras attached to him!!!
The beauty of including all those "sub-optimal" Bestow cards is that you can use them to enchant Athreos and buff him up for huge commander swings. Even if they find a way to get rid of Athreos, all those "auras" fall off and suddenly become an army of small creatures! If you have Spear of Heliod and/or Dictate of Heliod out, that army ain't so small anymore.
Some of these auras that can be placed on Athreos (or even Heliod or Erebos) can double as a ridiculously powerful defense. Enchanting Athreos with Pariah means that you are completely immune to damage until they can either get rid of the god or the aura. Put Soul Link on top of that for the ultimate in Grade-A dickery! That's right, any damage done to you is redirected by Pariah to your indestructible deity and Soul Link causes you to GAIN that much life instead. (Caution: your friendly neighborhood Red mage will cease being so friendly until he draws that Chaos Warp.)
2.) Tokens
Another route to victory in case the Voltron method fails is an army of Tokens. It's a very small sub-theme, but it's enough to surprise and overwhelm your opponents. Grave Titan can easily generate a few tokens. Heliod can use all that mana generated from Nykthos to pump out enchantment creature tokens to trigger all of those Constellation cards. Elspeth can continue spitting out an army indefinitely. The real winner (potentially) can be Storm Herd. There are plenty of ways to gain life in this deck. Can you imagine 40... or even more... 1/1 flyers? Those tokens you're making get to be a real threat when combined with Spear of Heliod and Dictate of Heliod.
REMOVAL
There are different methods of removal and control in this deck. Because of the need for enchantments and devotion, though, some of that removal comes not from spells, but from permanents.
Enchantment-Based Removal/Control
Banishing Light
Darksteel Mutation
Faith's Fetters
Journey to Nowhere
Oblivion Ring
One-Thousand Lashes
Soul Snare
Visara the dreadful gives the potential of repeated removal. Wrath of God can wipe a board and Extinguish All Hope can do the same while leaving your army of enchantment creatures. Silence the Believers, Path to Exile, and Excoriate (Mentions Heliod AND Erebos in the flavor text [theme points!]) act as spot removal.
Aura of Silence can both prevent your opponents from getting out mana rocks early and destroy a pesky enchant or artifact. SPhere of Safety is AMAZING in this deck, as your opponents will often have to pay 5 or more just for a single creature to attack!
C-C-C-COMBOOOOS!!!
1.) Athreos and Starfield of Nyx
Before anyone gets upset that I'm not using Athreos' incredible static ability, I want to assure you that that is far from the truth. With Starfield of Nyx making allyour other enchantments creatures, Athreos gets double duty. Now those Enchantments can be killed? Okay. I'll just get them all back with Athreos unless you pay 3 life. Ta-Da! Getting only creatures back with Athreos? Now who isn't maximizing his potential?
2.) This deck, Skybind, and Sun Titan
With all the enchantments in thsi deck, it can be fairly easy to trigger Skybind's ability. Targets like Grave Titan are fun, but Sun Titan is the real target here. Oblivion Ring, Soul Snare, or Aura of Silence in the graveyard? No problem. Just "blink" Sun Titan and get them back for use again. That enchantment based removal/control looks better now, doesn't it?
3.) Beacon of Immortality and Storm Herd.
This one doesn't need explanation. Huge life total. Obscene amount of tokens.
4.) Athreos/Heliod/Erebos, Pariah, and Soul Link
Refer back to "Means to Victory" under "1.) Voltron"
5.) Devotion and Divinity of Pride
Simply put, Divinity of Pride can single-handedly trigger Athreos' devotion. Plus it's a ridiculously awesome creature in EDH.
6.) Deserted Temple and Nykthos, Shrine to Nyx
Nykthos can create an incredible amount of mana, but combine that with Deserted Temple and you can double that up. Heliod's Cleric tokens thank you.
CONCLUSION
That's the basics of this deck. There are many more fun interactions in this deck. It's one of those that is totally janky, but surprises you. So much fun to play.