I would replace Asphodel Wanderer for Pharika's Chosen cause it doesnt really need the regen skill itself since there is Athreos, God of Passage , also remove one Swamp for a Plains since its too scarce.

Nightveil Specter looks good in this orzhov deck since most decks now offer black or white and you have the mana to cast exiled spells.

Odunos river trawler doesnt seem that good, since it is kinda redundant with Athreos, God of Passage and Rescue from the Underworld , and it can only bring back Nighthowler since it cant recover Erebos, God of the Dead if it gets exiled (wich is the only way to dispatch it since it is indestructible).

Tough this deck could make better use of some cards, it can stand itself by recovering many of its lost creatures or damage enemies, wich is good.

Thank you for the feedback, I'm just starting with black/white decks so this is really helpful.

Rescue from the Underworld doesn't work with Athreos, God of Passage if they DON'T pay the 3 life and the creature goes to your hand neither come back by Rescue from the Underworld only the creature that was sacrificed will return due to Athreos, God of Passage .

Card ruling for Rescue from the Underworld : "However, if the sacrificed creature is put into another public zone instead of the graveyard, perhaps because its your commander or because of another replacement effect, it will return to the battlefield from the zone it went to." I did check this out before I put it in, but thank you for the feedback anyway.

yes but Athreos, God of Passage puts it in your hand which isn't a public zone.

Hmmm... you have a point. What would you suggest instead of it then?

Obzedat's Aid

Tithe Drinker is a very valuable card for black/white. Early game stability, plus extort AND lifelink. I'd suggest throwing in at least two - perhaps instead of the Returned Reveler ? And since you're running Athreos, Bloodflow Connoisseur can become a brutal weapon, continually sacking your own creatures, just to play them again, buffing the Connoisseur each time.

Keep the suggestions coming, they are all extremely useful.

Sadly Bloodflow Connoisseur is not going in because it is in modern, but I will probably put it in when Athreos gets cycled out of standard.

Are you sure you don't want a Rescue from the Underworld in there? It's a great way to hit hard with that merchant.

I realised that it doesn't work with Athreos, because Athreos moves the sacrificed creature to my hand, which isn't a public zone therefore it doesn't return to the battlefield. It's an annoying loophole. I may still put it back in later though.

how about some nyxthos shrines

Not a bad idea, I'll have to do some testing to see if they work

Didn't work. It actually slows my deck down because most of my creatures don't use colourless mana, so it's useless in the early game and in the late game it's more of a "win more" card.