A good pair up with land kill is hand kill. I would seriously consider running mono black. With so many of your cards being split mana cards do you really need red? Out of Eventide is another land kill card similar to Poison the Well however the card is black/green split and it nets you 2 life. I recommend hand kill to stall them out long enough to lay waste to their lands. If you were to run mono black I'd suggest dropping the Manaforge Cinder for another cheap black creature.
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An interesting deck for sure. Is there a side board? My biggest concern is what happens to the deck when someone renders Necroskitter unplayable like Meddling Mage etc. I do not necessarily see an alternative win condition. Another concern is the lack of low cost creatures with wither which I think would bolster the deck early game. For good measure I would sideboard the Dash Hopes for 2 more Scar. If your deck revolves around wither you need to hit as many creatures early as possible.
A nice twist could be Yawgmoths Bargain. It would give you the draw you need at your pace late game. The obvious drawback is your draw rate is based on your life but your first win condition is Consume Spirit. Bargain would pair well with Lilliana's 2nd ability. Half of the shock would be that the opponent knows you can draw your card whenever you choose to do so. I am also curious to know if you would play conservatively or aggresively.