Theme: This is trible Liliana. The deck opperates exclusively with card's that: have Liliana in the art, are directly related to Liliana, are Liliana themselves, have Liliana mentioned on them in some way (quote, mentioned in the flavour text), or have a significance to the character as a whole (In this case there needs to be a significate relationship not something like adding Jet Medallion and saying "well Liliana is black and Jet Medallion is related to black spells". i.e. look at the 4 demons that signed Liliana's contract. Three of them don't mention Liliana, but they're so closely tied to her that they're in the deck [See Substitutions for Grislbrand explanation]).

Substitution...
Vilis, Broker of Blood (better known as Grisl Daddy-2): He is present in the deck because Grislbrand is banned in commander. If Grislbrand wasn't banned he would be in here, and I would pay the 11 grand to get a Grislbrand, because if he wasn't banned he would cost 11 thousand dollars. Essentially to keep part of the theme in tact I subbed in Baby Daddy Grislbrand 2 to supplement unusable pieces.

Land base...
Lands are irrelevant to the theme. There are 2 lands that reference Liliana and they aren't in mono black. Therefore I remove the restriction to lands. This also allows the deck to not lose instantly against any deck with green. Objectively you could just run 40 swamps and call it a day, however the upgraded mana base will actually keep this deck usable. You can still have fun with the core theme and actually still play the deck with this upgraded mana base.

Sideboard:
The sideboard contains solid upgrades to the deck if you wanted to remove some of the other irrelevant cards in the deck, but it breaks the theme.