It's obvious that WotC has been pushing a Delirium theme in GB for SOI Standard. This list uses the best of the best in tandem with many cards that can activate Delirium swiftly and take advantage of the crazy value from these cards to push through for a win in this efficiently costed midrange deck.
The overall cost of the deck is a factor to me, although I will say this deck isn't entirely a budget build.
I did consider
Liliana's Indignation
, however, after doing some math, I figured that (after the first black invested) I would have to spend three mana for every two damage dealt to my opponent. That is a terrible mana -> effectiveness conversion, especially for a deck that looks to win with board presence. The fact that it puts those cards into the yard isn't good enough because it costs far too much to get that job done as well as allowing my deck to flip me a double birdie by only putting one or two card types into my yard.
As for certain cards like
Corpse Churn
that proactively add cards to the graveyard, I like these cards in a Delirium deck a LOT. However, these cards generally don't do quite enough for the tempo loss in a list like this. One of the concepts that I am attempting to invoke with this deck is, "Delirium rocks, but not having Delirium in time is okay too". You'll see that many of these Delirium cards do not entirely rely on Delirium to be effective.
In essence, the deck doesn't need Delirium early, but having Delirium early makes the sick draws happen (I keep emphasizing early because, in a deck that covers this many card types, getting Delirium is not a question of "if", but a question of "when").
All creatures are fine without Delirium and simply get better when this mechanic is present. Because of this, our deck can function just fine without being able to reliably trigger our namesake mechanic and simply improves with inevitability.