This is one of the Mutate commanders in Ikoria. It's a fantastic reanimation engine. It's Ultimatum should be a game-ender. It's enchantment has multiple ways to help you, including life gain in case your black cards cost you too much life.
This deck needs to drop lots of card into the graveyard and has a solid Companion in Kaheera. I would add several reanimation spells in the vein of Cauldron's Gift.
The flyers are mostly going to be White and Black.
Green helps to feed the graveyard.
Ikoria also has some new graveyard feeder spells.
Here are some great cards for this deck in the current Standard.
You will need to protect your graveyard.
The Mythos card for this wedge is reasonably powerful since it can destroy a nonland permanent (and not just a creature as Murder would).
There are other cards in Aban or that can be added to Abzan, but I don't think these fit what this deck is doing.