I would take out the liliana's from side, as well as the cards u suggested. they don't fit with ur theme

heres an alternative sideboard:2 Witchbane Orb 1 Mutilate 2 Cavern of Souls 2 Searing Spear 2 Pillar of Flame 1 Griselbrand 2 Killing Wave 2 Rakdos's Return 1 mikeaus, the unhallowed

Doesn't Heartless Summoning ruin Master of Cruelties by making it so he doesn't deal damage anymore? Which means that they can block him for free?

yes and no. If the board is empty he can still swing at 0/3 and as long as they don't have a way to block they still go down to one life. he can't run through creatures anymore but he is still a creature they want to target with burn or kill spells, saving another creature from them in the future. at least that's how i look at him. plus heartless doesn't always come up. and with heartless he comes out on turn 3 instead of 5.

I play a similar deck and I have to say that Necropolis Regent is better than Reaper from the Abyss in most situations. She is essentially a win condition all on her own.

I love Reaper from the Abyss because for this deck he becomes control. once he's out almost every end step I have the chance to destroy a non-demon creature. plus the combo between him and Nefarox, Overlord of Grixis is insane! Every time Nefarox, Overlord of Grixis attacks they sac a creature and then block or don't and then on end step I destroy a second creature. Necropolis Regent would make Nefarox, Overlord of Grixis more powerful but with my demons being such high drops, they usually are against a crowded battlefield.

Disentomb and (especially) Crypt Incursion aren't really good choices to put in the deck. You're much better off throwing in more removal like Searing Spear and Pillar of Flame in their steed.

Crypt Incursion usually helps more than people realize but I 100% agree on Disentomb . I think ill put in one Pillar of Flame and one Searing Spear to see which works better in the deck. Thanks. :)