During say a standard, etc gameplay yes, But the way Commander works are you limiting yourself for cards based on your Commander right? so technically you can only play black/green cards. Having green/white like that technically wouldn't work even though you could still pay green to play it because your Commander is only black/green
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No, actually it's not fine. It's like that for a reason. You can run Crypt Ghast in a mono-black deck fine because the white mana symbol is only a reminder. In Wilt-Leaf Liege case - it's the physical cost of the card. This means it would be illegal in a Golgari deck. But go-ahead and run it, you'll be told to remove it the first time it gets played at a LGS or via online play :)
Cannot run Unmake in this deck - Sheoldred is mono-black only my friend
You can't run Wilt-Leaf Liege in the deck due to the half-white cost of the card. You're also really heavy into the lands. You could probably drop 2 lands and Wilt-Leaf Liege and add in more utility. Heroic Intervention, Veil of Summer, and Sudden Spoiling would be all good adds to the deck. Low cost and can be useful on attack and defensive.
You're better off running Chainer, Dementia Master over Belthor. With Balthor you can only get him used once as his texts state you have to remove him from the game to get it. With Chainer, you just have to pay 3 life and tap 3 black mana and you can return any creature card from any graveyard to the battlefield. - With Chainer, this ability can be done at Instant speed meaning it's a little more difficult to stifle the ability as you can just repay into it and do it again.
Because you would only be able to get your Commander to be used maybe 3 times at most before the mana cost gets too high. Chainer you can just keep reanimating him over and over and over again for literally 3 mana and 3 life per reanimate. Netting you in the end more use of him in your 99 than over him as your lead.
You're better off using Xiahou in the 99 and using Chainer, Dementia Master as the Commander.