This is really expensive for the drawback. If it only affected opponents I could see it but as it stands, too pricey to encourage play.

No idea how this card went so long without an edit, especially since I’ve had it in my physical playtest cards with this current wording for months.

Is there a R/B slot this could slide into? Seems like it'd be more palatable (and exciting) at an efficient cost of , sort of like a cracked out Armadillo Cloak.

As is, it's alright, but most its analogs (like Demonic Appetite and Oni Possession) are cheaper AND positioned at lower rarities.

With Houlding on this one: that drawback is still pretty harsh for the benefit. Even if you do cast this on turn 3, you're probably not going to ride this to victory. If not multicolored, then 2BB seems appropriate.

Has an interesting interaction if cast on an opponent's creature too.

Also got to agree that this seems steep compared to the common Demonic Appetite. Besides that, though, I wonder if trample is appropriate for a card like this. If the point is that I'm slowly losing to my own ability, then maybe you want to let your opponent chump block it? Maybe it's just me... that's possible. If I was to do that, though, I think I'd have a clause that stopped most continuous blocks. Something like "When a creature enchanted by ~ deals damage to a creature, exile that creature." Don't mind me... I'm just thinking out loud.

Oh, no worries about thinking out loud. These are all really good points. And to be honest, I'd completely forgotten about both of the forementioned auras — likely because I was never enticed enough by them to pay them any attention. Which says something about this kind of enchantment.

Regarding going R/B: ideally, yeah, it probably would be. I already have the angel slotted in for R/B rare though, and dammit, I really like her.

The goal here is to more or less recreate the “Lord of the Pit” analog, as nearly every base set has that one huge marquee demon. Soradyne doesn't, and the story doesn't really lend itself to one. It does have this disease though that turns veterans into raging psychos though, so here we are.

I'll take another hack at it. Check back tomorrow...

What if it were simply an enchantment rather than an aura? Something more akin to the recent Homicidal Seclusion, or earlier concepts like Death Pit Offering and Eldrazi Monument.

Crossblight Miasma
­
Enchantment
At the beginning of your upkeep, sacrifice a creature you control. If you do, put a 5/5 black Mutant Horror creature with trample onto the battlefield.
At the beginning of your end step, sacrifice a land. If you can't, sacrifice Crossblight Miasma.

I can't really remember what the Crossblight was conceptualized as, but it seems like there's probably a pretty straightforward and enticing top-down design that could built in that mold.

That's a pretty cool concept. I'll have to ponder that in relation to the set/story.

I'd been thinking along the lines of "enchanted creature gets trample and +1/+1 for each land and creature in your graveyard" along with the sac-a-creature-and-a-land thing. Does crazy things in a mill environment, works well with other sac outlets and effects.

From a purely story angle though, Tarkot's Cross is basically Gulf War Syndrome. It's a mystery ailment that affects veterans from a specific battle (Day of Silence) and has no apparent cure. I'm a little worried about the idea that this brutally destructive condition can be stopped with a simple Disenchant effect.

Thinking some more about Houlding's enchantment that makes tokens. I think this might actually be the best way to go if the Crossblight doesn't actually have a cure; killing the enchantment doesn't actually cure the Crossblight, it just stops the accelerated emergence of it, and I think that’s pretty reasonable.

Solving the execution is still a question though.

An enchantment that amplifies the “bloodlust” of the Crossblight as it emerges in a population. Has a strong effect that plays nicely with a number of other very accessible cards in the set. How’s that?

Excellent.

What if the terminating trigger were "At the beginning of your (or each) end step, if you didn't sacrifice a permanent this turn, sacrifice Grip of Tarkot's Cross"? The gameplay would probably be similar, but it would put a sort of onus on the player to sculpt their deck to fit the enchantment (and the philosophy of Tarkot).

That's decent, but it does two things I’m not sure I want to do: 1) It gives the user an out to not sac a creature to it, and 2) It places the “upkeep” sacrifice at the end of the turn where people are less likely to look for and/or remember it.

I really like the flavor of this suggestion, I j

(cont'd.) Just think that it starts getting into the “memory issues” realm.

Is there a particular reason it's important that the player sacrifice a creature? Just to create an entropic effect?

As to memory concerns, that's understandable, though the sacrifice of a permanent is a fairly notable circumstance.

Partly for the entropic effect, and partly as a call back to black “mainstays” like Lord of the Pit. Having a “sac a creature” upkeep cost makes it feel familiar, puts a trigger to make counters right at the start of your turn (when it gets you the most value), and creates a sense of peril and tension. All three are things that work as nice mechanical metaphors for the madness caused by Tarkot’s Cross.