Deck looks really good. I am a zombie player as well, Mono-black. I recommend Grimoire of the Dead for sure.

Undead Alchemist is not as good as you think. It prevents you from doing Commander damage and increases your opponents' life totals to 100 rather than 40.

Liliana of the Dark Realms, Archetype of Finality, Animate Dead, Erebos's Titan, Xathrid Necromancer, Ashiok, Nightmare Weaver, Phenax, God of Deception, Diabolic Tutor, Ashen Powder. Could you upvote my Brago Azorius ETB?

Vortexflame I don't get your point where you're saying Undead Alchemist increases opponents life to 100 instead of 40 points. However, I will possibly switch this guy for Grimoire of the Dead since I think it would be a better fit in this deck.

Undead Alchemist prevents actual damage from being dealt. Instead you mill your opponent, whose library is 100 cards. That's why it's not a great idea to use in this deck.