One tried-and-true way to win in Standard is to lean on Ishkanah, Grafwidow. The giant Spider with all of her friends can stabilize from many different board states to take over a game.
This particular version of Delirium has a full playset of Ishkanah. We’re not messing around here. Plan A and B both revolve around Ishkanah, so it’s important to be able to make sure your graveyard can cooperate.
The usual suspects, Grapple with the Past and Vessel of Nascency, are here. Both help turn on delirium while digging for Ishkanahs. Grapple with the Past can even return a fallen Spider for more value. By playing a G/R Delirium deck that splashes black instead of only G/B, you get to make use of Cathartic Reunion. This adds more sorceries to the graveyard for delirium, but also can make sure that you can turn on delirium by turn 5 consistently.
By playing a heavier red base with just a little black, you also get to add sweepers. Radiant Flames is the big one. When Radiant Flames is good in the format, Jund makes more sense than G/B. Being able to wipe out Spell Quellers or all of the creatures in a Mardu Vehicles deck is an effective weapon.
With just a smaller black splash, Grasp of Darkness, Murder, and Ruinous Path aren’t quite as appealing. You have the Radiant Flames, but Harnessed Lightning instead fills in for the removal suite. This is a very real downgrade from G/B.
The creatures are also going to be quite different. Without early black mana, Grim Flayer goes out, and Sylvan Advocate comes in. Some players already prefer this swap, but Advocate is the better creature when you want to be more defensive. If you’re playing to the late game, the value from a card like Goblin Dark-Dwellers really shines. There aren’t too many spells to flashback, but with self-mill, the graveyard should be pretty stocked. Grapple with the Past to get Dark-Dwellers to bring back Grapple with the Past is a pretty nice way to take over the late game. Using Traverse to get the Goblin to bring back Traverse for Emrakul, the Promised End or Ishkanah is quite nice.
For a small investment, Dragonmaster Outcast gives you a late-game threat that can take over. It can come back with Grapple with the Pasts as well.
Liliana, the Last Hope is another way to load up the graveyard and bring back these big creatures. I really don’t love it in this deck, however, as the double-black cost is really prohibitive as a splash. You aren’t going to be able to play it early, but its effect is still worth it later on.
The much hyped Chandra, Torch of Defiance is a planeswalker you can cast early to help take over the game and then run away with it in card advantage. This planeswalker is finally seeing the rise in popularity that she deserves.
I would probably look to add a creature like Pilgrim’s Eye to this deck, especially without having a single artifact in the deck. With a few minor changes, I think Jund Delirium can be a force in Standard!