3 To the Slaughter is probably overkill, even if you find yourself able to reliably turn on delirium by the time you want to cast it. It's kind of so-so if you just get the edict effect; to be good you really need to snag a planeswalker. It's fine in the sideboard and maybe as a 1-2of in the main, but there are too many decks running around right now that have interchangeable X/3s for 3 mana, and they usually have an ETB effect, meaning that you lose out on the exchange if you only get a creature with this. Especially since they get to choose. Murder is more reliable creature removal for the same CMC, and Ruinous Path can take care of planeswalkers decently enough since you'll be tapping out on your turn in this deck most of the time.

If you care about delirium enough, Crop Sigil and Grapple with the Past are worth considering, especially the latter. The former you only really want in a dedicated delirium deck, while the latter is just a good way for you to get a creature or a land back if you hold up mana and don't find anything worth killing on their turn. You can get back any creature or land from your graveyard, not just whatever the card reveals. This might make it worthwhile to run a single Blighted Fen as a hedge against control. Hard to say at the moment though.

Permeating Mass is not a card you want in my opinion. You have too many creatures with useful abilities and you will find yourself occasionally needing to block with your Kalitas or unflipped Den Protector against their 1/3 Mass. It's only 1 damage, but the problem with the Mass is that it's a repeatable source of 1 damage as long as they know you won't block it. And you probably don't want to waste one of your few removal spells on a 1/3. This guy will be annoying enough with other people putting him into their decks, I wouldn't make the mistake of giving them one for free. You can win with beefy flyers and you have numerous ways to gum up the ground as it is, so this guy doesn't do anything that your deck can't already accomplish.

Gnarlwood Dryad is fine, probably better in a more aggressive deck, however. For gumming up the ground you already have Hangarbacks and Sylvan Advocates, so I'm not sure what he does specifically that you can't already do. Especially since your deck in its current configuration won't be too quick to turn him into a 3/3, especially with all the bounce and exile in the current format.

Grim Flayer is potentially very good in the abstract, but has the very serious problem of being thrust into a format dominated by X/3 creatures. Your current deck configuration doesn't have enough removal to allow him to attack reliably on turn 3, and if you rely on him for activating delirium it's essential that you do so as often as possible. He has good synergy with Drana, however. But that doesn't pump him up against a Sylvan Advocate until turn 4 at the earliest, assuming that they don't deal with either him or Drana. I think this guy will find a place in Standard soon enough, but I'm not sure this is the deck.

Mournwillow is completely awful except in some sort of hyper aggressive delirium deck. I don't think that deck will exist at all, and even if it does I don't think this one will look much like it. Inconveniently, creatures with power 2 or less tend to become less relevant about the time that delirium gets active. So he's effectively a 3/2 with haste for 3 most of the time. Even against a deck full of small creatures, by the time you have delirium active your opponent will have +1/+1 counters on one or more creatures, an Avacyn, an Always Watching, or something similar.

Ishkanah, Grafwidow seems promising to me. Turn 5 is about when you can start to have delirium online reliably, and the effect is strong. It's an ETB, so if your opponent bounces her with Reflector Mage to allow their Avacyn to attack, you still get some value when you recast it, and the spider tokens can chump fliers in the meantime. She reminds me of a toned down, conditional Hornet Queen, which is still high praise because the latter card usually won the game if your opponent didn't have an immediate answer.

I am convinced that, even in a dedicated delirium deck, Whispers of Emrakul is a sideboard card at best, and maybe not even that. A lot of people who seem to be so hyped about it forget that one of the things that made Hymn to Tourach so good was that the decks that played it reliably stripped two random cards from your hand on turn 2. Maybe turn 3 at the latest. This is early enough to get lands and strip the build around cards that most decks rely on playing turns 3 and 4 (in standard, think of Reflector Mage and Gideon, Ally of Zendikar). By the time delirium is active (turn 5 or later), your opponent may not even have 2 cards in hand. If they do, and they have open mana, one of them is likely an instant that they will cast in response (killing one of your creatures, CoCo'ing you, Secure the Wastes for 4 or so, etc). Before delirium, your are playing a 2 mana sorcery to grab a random card from their hand. This is almost always going to be worse than Transgress the Mind, which has the triple upsides of (1) exiling the card, (2) giving you considerable choice over which card is exiled, and (3) letting you see their entire hand. That last item is what people are most overlooking when evaluating Whispers of Emrakul. Half the value of Transgress is the information you get, and Transgress is barely played as it is.

Final thought: I think you need to decide how deep you want to go on delirium. Just because there are promising GB cards that have the word "delirium" on them doesn't mean you should put them in your deck. Higher CMC delirium cards require less setup, so something like the spider queen will stress your deck much less than a card like Grim Flayer or Gnarlwood Dryad will.

Odyssey, thank you so much for all of your help as always. Your thoughts on these cards are immensly helpful, and I don't think that any of the many decks that I brew would be nearly as strong if it wasn't for you. Your comments are allways extremely thought out and have obviously taken a long time, so thank you.

I agree that I needed to figure out how delirious my deck should be, and the deck might just be trying to do too many things at the moment. It's limited in how you can build delirium with only ~20 creature slots, and delirium is naturally a slower strategy. I can try to build a fast version of this deck, but I've found that if I'm building a deck with Drana, Liberator of Malakir, the deck has to be decently fast.

I'll keep looking at this strategy, but I think more of my energy will be put towards Keywords.deck (SOI Standard, Building for EMN), which I'm currentlly at an impasse with which cards to replace with new ones!

Thank you once again to all who have helped with this deck!