DedWards

It's like that according to my store's Event Organizer, though I have proven him wrong in the past. If you can find a definitive (or close to) ruling on this that proves him wrong, please share.

Pretty good take on the idea.

Now, I need to check the sequencing, but /if/ the sequence works out favourably, a 1 of [Ob Nixilis, the Fallen] to fetch off sacrificing [World Shaper] to [Eldritch Evolution] could make for a decent alt finisher.

Scrap that, it won't work. The sacrifice clause on [Eldritch Evolution] screws with the idea. The sac is part of the cost, so [World Shaper]'s dies trigger will be put on the stack above [Eldrich Evolution]'s search.

Dark Petition is a good card and worth considering here. If you stick with Mastermind's Acquisition, I recommend moving 1 Tree of Perdition and 1 Triskaidekaphobia to sideboard to protect the main deck from exile effect like Surgical Extraction or Lost Legacy.

Other card suggestions I have:
> Victim of Night - Death's Shadow is a big threat in the format and Doom Blade can't touch it. I would suggest Go for the Throat in Doom Blade's slot, but Affinity / Robots is a thing too. Victim of Night hits a lot more im the format than the other two do. Grasp of Darkness and Dismember are more decent options.
> Godless Shrine - This can replace a few of the basic Plains and opens up Verdant Catacombs / Bloodstained Mire / Polluted Delta to replace Evolving Wilds. The option of coming in untapped is a big advantage.
> Damnation - Go wide / untargetable creature strategies will be a problem. This or Wrath of God or Day of Judgement will go a long way in keeping you alive long enough to combo off, with Damnation being the best as you're currently heavily skewed to black. Dusk (Dusk // Dawn) and Languish are options that keep Tree of Perdition alive while wrathing.

It's actually a trick I learned while trying to make mono red Dragonstorm work under the current Modern legalities. Maybe I should revisit that deck sometime...

Panorama comes in untapped and can add {C}.it's in fot mana fixing /IF/ I need fixing. Need that untapped mana in the early game to optimize the land destruction.

Oh, and Blood Moon is getting reprinted in Masters 25, so we could see a drop in the price tag

I'm not convinced Bloodbraid is a good thing for Ponza as it can hit so many not-so-great things that can not be taken out of Ponza, like one of the mana dorks or Mizzium Mortars / Bonfire of the Damned. Just like how Goblin Dark-Dwellers affects what you include in your list, Bloodbraid will affect a lot of the other card choices. While I'm not a fan of including Bloodbraid, a lot of people are. In the Primer I used, the people are working on including it, so take a gander there (check the latest pages).

As for budget reasons, I personally think that Ponza is one of the cheaper competative decks in the format, despite budget restraints. What I mean is that some cards may look like "budget options", but are in fact not. Because of how uniquely Ponza works, it often does better without all the "expensive" cards. That said, some expensive cards are very good in Ponza; expecially Chandra, Torch of Defiance (which I should have 3 of at the end of March :D ).

Primer:
https://www.mtgsalvation.com/forums/the-game/modern/developing-competitive-modern/220790-rg-ponza-modern-land-destruction

Ignore this, I was being stupid.

My bad. Fixed it.

The biggest down side of Megrim / Liliana's Caress based discard decks is the opponent managing to keep their hand empty. There's two ways to combat this:
1) Include Rack style effects to continue dealing damage while their hand is low / empty.
2) Include Howling Mine type effects to increase the chance of the opponent having stuff to discard and helping you draw into more discard. Bonus points if you can use this option to make Dark Deal better than it already is.

How good do you think Nykthos would be in a Shadowborn Apostle + Demons deck? My idea is that the large number of Apostles can sypply a decent devotion count to play any demons you unfortunately draw.

With that many reoccurring creatures, I feel there's a need to abuse the recursion. But I can't think of a decent option that doesn't pull away from the Devotion.
Have you thought about including Phyrexian Obliterator?

Mogis's Marauder to give the team Intimidate?
Maybe some X drain spell to capitalise on Nykthos mana, something like Consume Spirit or Profane Command.
And depending on how important Nykthos is / becomes, one or two Expedition Map could be useful.

Tasigur is an... interesting inclusion. The only reasons I can see it included instead of a 4th Angler is it costs {1} less than Angler and it has a different name for things that care for names (Surgical Extraction, Meddling Mage, etc.). With 0 blue sources and only 1 green source (Stomping Ground), you're definitely not going to be able to use Tasigur's activated ability.

Have you seen the Hollow One decks popping up in Modern? They could hold a few ideas that could help improve this deck.

Soulblast is iffy here. Most of your creatures kill themselves at the end of turn, so they're not around to be sacrifices for Soulblast. And Soulblast costs a lot of mana, you should be winning / have won long before you have the 6+ other creatures costs for your "Mega Fling".

The Mega Fling idea is nice, just impractical.

Mimic Vat? Gets you extras of your "dies at end of turn" creatures.

That's an awesome one. Will suggest it to the friend I designed this for.

The argument can be made that if you already have it, it's effectively free :p

Ghostly Prison doesn't care for hand size, allowing you to slam it early and hold onto cards to drain the opponent with while waiting on Tainted Remedy. It's more a delaying tactic than anything else. Most importantly, Ghostly Prison is cheaper ($).