Have you considered cycling in the deck? Xiahou Dun says black card to hand, not creature. That opens up design space. There aren’t a ton of black cycling cards (20), but what’s there can be pretty good- Twisted Abomination to get swamps to power some of the Voltron equipment for example. Decree of Pain is just an all star. You can keep getting engines though, like Unearth or Undead Gladiator.
Pass on Voltron, the general doesn’t lend itself to the build up style. Coalition Relic is a little too bland in my mind for a mono colored deck, but it does help you hit the BB costs easily, but so do the swamps used for Coffers. I say pass. Lens is too risky. Pass- it will just get tanked by someone and cost you a card and a land.So you want to find nonbasic lands? Have you heard of Expedition map? Coffers works well with swamps- Armillary Sphere.To help get back Xiahou Dun:Oversold Cemetery– no lost draw step.Mimic Vat– stick him in it and constantly replay him.
I feel the best direction would be focusing in big mana/control. This opens up all stars like army of the damned, curse of the cabal, temporal extortion and drain life effects for finishers. (if you’re feeling mean, helldozer is amazing)Nirkana is both black and a creature, making it extremely easy to recur…it will draw removal like a lightning rod, although I feel that it is worth it for the effect it brings. Caged sun is far too good to pass up. Gauntlet of power does not seem worth the effort since it benefits all black players and dies a quick death.I see no reason not to run crypt of agadeem. It costs some tempo but the upside can be huge and it will always tap for at least one…
Evergladesis good I have always been a fan of bounce lands for creating an additional virtual land slot. Lotus vale is a trap all it takes is one player feeling a little vindictive and it’s food for a dust bowl. Not really a fan of lake of the dead.Liliana I feel is very strong in a deck like this. She can be recurred with you general, grabs a land each turn and is good removal.
I think in mono-black you need to look at the pestilence guys: pestilence demon, crypt rats, and thrashing wumpus. These guys are awesome with mana and pro black. The SoLS really helps make this work. Get the dude, nuke the board, crash into someone get the general back, then go nuts recurring something every turn.
What about Nim Deathmantle? I love this guy and it seems like a champ in this deck. Sac Xiahou Dun, pay 4, rinse and repeat. Plus the extra +2/+2 can be significant from time-to-time.Lake of the Dead, Lotus Vale, Cabal Coffers, and Crypt of Agadeem are all pretty lucrative targets for land-hate, why not run Crucible of Worlds? It interacts especially well with
Lakeof the Dead and Lotus Vale, returning the lands you sacrificed with them. If you did that then adding in Buried Ruin might be worthwhile because it protects Crucible which protects the Ruin which…etc, etc.