Hey just throwing this out there becauase it would be a totally different deck if you did this.
Shadowborn Apostle is great with Athreos because you are either doing so good damage or you are getting to use their ability multiple times. I would be willing to bet though that your opponents would pay the 3 life for at least 1 of them though so you can't do it right away again by paying 7 to drop 6 and use the ability. That is where
Secret Salvage comes in
But it looks like you are doing the aristocrats idea (which is totally fine).
You're already running
Urborg, Tomb of Yawgmoth, so why not
crypt ghast? It isn't as comboy as
Urborg, Tomb of Yawgmoth and
Cabal Coffers, but it is pretty kewl.
If Razaketh turns out to be too slow,
Grave Titan might be a decent replacement in terms of power level. It doesn't do the same thing though. Maybe replace
spawning pit with
Grave Titan? It is a lot more mana but
Spawning pit seems like it requires so much to get going. Also
Sun Titan wouldn't be a bad idea. Both of those Titans have ETB effects as Judaspriester pointed out are good to have with your commander. And if your opponents don't give them back to you, you have your own
reanimate package.
Entomb and
Reanimate are wonderful cards, either together or by themselves, and
Unburial rites seems like a good card as it can be used twice.
Ophiomancer is one of my favorite black token generators, along with
bitterblossom (expensive) and
Ogre Slumlord.
Okay so I run
greed and
Necropotence in my
Ayli, Eternal Pilgrim deck and I much prefer
Necropotence because it is half the life and no mana. Trust me the "draw backs" that is has aren't noticeable at all. Instead of drawing 1 card on your turn, before your opponent's endstep you activate
necropotence to fill your hand back up to seven. If there is a specific card you are looking for, you can dig really deep. i drew 30 cards off it in a turn, looking for
Teferi's Protection because my opponent had cast
mystical tutor for
cyclonic rift.
And if you are going to run
necropotence, i have to suggest
Bolas's Citadel too because it is SOOOOOOOOOOO good. This card has single handedly won me the game multiple times. And with
necropotence, you can
exile the top card if it is a land.
Pitiless Pontiff would be a nice sac outlet, not that you don't already have plenty. The deck looks fun. I would add a few one shot draw effects like
sign in blood, but that is because I absolutely love the flavor of paying life for cards. Using your life as a resource, so that is just me.