This looks like a lot of fun. Ertai decks are great.

I would say you might want a little more in the way of sac fodder, because without some of your more important pieces in play, you might not want to sac creatures. You have tons of things that benefit from sacrifice, and the persist/undying certainly mitigates those effects, but some token producers could be very helpful.

I'd suggest Teysa, Orzhov Scion, as she does double duty as removal and token generation. She isn't benefiting from your blue, but getting a black creature back like Geralf's Messenger plus a token with flying is pretty great for a three-drop permanent. I'd suggest swapping her with Gravelgill Axeshark, who isn't doing a whole lot here for a five-mana slot.

If the funds permit, I would remove Animal Boneyard and replace a basic land with High Market, then work in Field of Souls. This thing puts in a lot of work--even more so with Teysa, but on its own it is pretty great.

Altar's Reap is a great little card, but I feel like the new Vampiric Rites has better commander potential. I am also a big fan of Dark Prophecy in decks that have enchantment removal to take care of it if it becomes a problem. Though Necropotence is still my go-to draw engine. Either of these would also make a suitable replacement for Vivisection. As a four-drop sorcery, it leaves a lot to be desired.

NoSoyYucateco, thanks for these really great advices. I will definitely put in Teysa, Orzhov Scion and High Market, which look like great synergy. I haven't known of Vampiric Rites yet, so that card will replace Altar's Reap for constant CA, nice.

Necropotence is propably the best carddraw card for black, but takes , which makes it somewhat difficult to consistently be played in early game. The same is true for Dark Prophecy and also for Geralf's Messenger, which is already in the deck. But I'll consider them for sure.

With your aid, the deck will soon be playable and competitive. Thanks a lot, mate!