Sadly if you're removing abilities you also need to give creatures a power and toughness, as Turn to Frog / Sudden Spoiling / Polymorphist's Jest demonstrate. Otherwise the Tarmogoyfs and Sutured Ghouls won't know how big to be.

Technically, Tarm and Sutured Ghoul would be a 0/1 and 0/0 creature, respectively (the same p/t these two creatures have in the graveyard, when their text isn't turned on.) The Sudden Spoiling problem isn't 'the rules can't handle it' so much as 'it really bothers some players and confuses others'. I'm not even sure if really simplifies things, since setting power and toughness is confusing it its own way.

That said, Alex is right that that's the way Wizards does it currently. And they probably do it for reasons, which involve surveys as opposed to opinions.

fair enough.

Jmg: That used to be the case at one point (see Selfless Exorcist's reminder text), but it's not true any more (that reminder text has the unusual distinction of being flat-out wrong now: a Tarmogoyf card or Fungal Behemoth card etc has its P/T defined in all zones, though obviously Sutured Ghoul will be a 0/0). Abilities are removed in layer 6, and P/T is set in layer 7a. (I think; I'm working from memory here.)

I think you're half right, with my apologies. I was looking at the example in the comprehensive rulebook and came to the wrong conclusion (They were talking about Lost Order of Jarkeld which requires you choosing a player. I only paid attention to the 'being in the graveyard part'. My mistake.)

Rule 208.2a however states: "...If the ability needs to use a number that can’t be determined, including inside a calculation, use 0 instead of that number."

Or, in other words, the fact that they cleaned up how Tarm and company works doesn't mean the rule still isn't in place.

604.3 spells out that CDAs apply in all zones; but 208.2a provides a default for cards like Sutured Ghoul or Lost Order of Jarkeld where the CDA refers to some variable that's unspecified.

But my point about the layers was accurate (I even got the layer numbers right from memory). If Tarmogoyf loses its CDA in layer 6, its power and toughness will be undefined. Would that mean the stars are treated as 0s, making 208.2a treat it a 0/1? Or would the game just say "I have no information on what your toughness is", making 208.2a treat it as a 0/0?

It's possible to get somewhat similar with a Lost Order of Jarkeld on the battlefield without having had any opponent chosen. (Perhaps it was Cytoshaped into an Ashcloud Phoenix, died, came back face down, then got turned face up by Break Open. I didn't say it was likely... Or maybe you just turned something else into a Lost Order using Cytoshape or Vesuvan Shapeshifter.) There the "number of creatures the chosen player controls" will be 0, making the Lost Order a 1/1. So probably a Tarmogoyf that had its CDA removed would be a 0/1.

So yes, I think the rules could cope with an effect that removes CDAs without setting P/T. But Wizards have so far avoided doing so, and I agree that it's likely they have good reasons.

Did I miss a description of Misinvoke somewhere?

It's a mechanic from the last set. I haven't defined it on the mechanics page

It says: you may exile it as it resolves, if you do, cast the back without paying its mana cost.

So, what's the difference between Misinvoke and a modal spell? The latter is easier to understand, and doesn't require DFCs to implement.

This spell needs to resolve for you to cast the other side.

The reminder text says "instead of letting it resolve." It looks like your intent is that this gets all the way to resolution, at which point you instead cast the other side. What's the point? What's your intent?

Even setting my confusion aside, blue does not grant indestructible like this.

This flavour is supposed to be that the caster tries to cast the front spell, but instead casts the back spell "by mistake"

Mechanically there's two spells cast, the first spell is exiled if misinvoked, and the second spell is cast from exile.

But unless Stifle is involved, how does that mechanically differ from a split card? It's not going to feel like it's "by mistake" if it's your choice.

I guess this triggers Prowess twice, but that's the only benefit I see here. It just send confusing for no benefit.