Suppose someone is a target of a supernatural effect of high enough level (and one not tailored to the target) to induce "instant" warping. Does the spell affect the target first? Does the warping affect the target first? Do they both affect the target simultaneously? While this is usually a rather academic question, it does have some practical ramifications.
For example, a Hermetic magus who is Prone to Twilight rolls for Twilight when receiving a single warping point. While in Twilight he is immune to all forms of damage. If someone where to target him with a Clenching Grasp of the Crushed Heart, could he slip into Twilight and avoid death?
As another example, a diabolist can use Debauchery + Phantasm to turn himself into a phantasm with Infernal Might. In such a form he is immune to warping. If the infernal effect is high-level enough, it causes "instant" warping ... does the effect manage to protect the infernalist from its own warping?
Twilight Prone doesn't work how you think it does. A Hermetic magus doesn't check for Twilight from just receiving a single Warping Point. So there is no need to check once a year for Longevity Rituals, for example, nor every time a high-magnitude effect hits the magus. It triggers based on single botches when casting. That is just one of several ways to get a single point of Warping.
You are right, I got confused looking at Monistic Mysticism from the Church: "The character now suffers from a similar effect to that of the Hermetic Flaw Twilight Prone — she must test for Divine Ascent when only a single Warping Point from any source is gained." Indeed, it says similar, not identical. But the question remains valid.
The effect causes the warping - so your hypothetical magus takes the Clenching grip of the Crushed Heart, and dies. His corpse is not affected by Twilight, as he is dead. If he was under a Death Prophecy, then your agonisingly heart-clenched magus gets to see if they go into Twilight.
The Infernal magus who turns himself into a being with might temporarily - they gain the might, then suffer the effects of warping - so as they now have might, they don't suffer any effects. It's a modest blessing, but they are now at the mercy of Hermetic magi with Demon's Eternal Oblivion so it may not always be the wisest choice.
Being Might-stripping spells aligned to specific Realms, if that magus is affected by DEO means that he probably deserves that and more. And also that the term "blessing" should be preceded by the word "infernal"!
I've been considering this timing recently. Is there any reason they can't hit at the same time? Entering Twilight from Warping Points isn't necessarily instantaneous. If it's resisted, it takes two minutes to deal with it. How much of those two minute are you around before entering Twilight if you fail to resist? If you don't try to control it, you enter faster, but it's only significantly faster than two minutes. It has to be enough time to be able to make a conscious decision to try to resist or not since that decision is specifically mentioned as being made. So it's not instantaneous.
Personally, I would have both hit at the same time, but I would have Twilight be entered after a moment if not attempting to control it. This solves one problem with a spell that delivers Warping Points as you pick them all up together. Meanwhile, saying Twilight issues arise more slowly than physical damage issues and other stuff seems consistent with the rules and provides a meaningful order.
TBH the only time in my IRL saga a player warps is either:
because of a heal spell
because of a teleportation spell
because of some powerful support spell.
In these 3 cases, the warping cause is a "friendly" magic. I have never seen an antagonist magus tries to use high level magic because of penetration issues.
I have however seen antagonists use variant of CrVi to make characters warp, with great effect but then, the effect is the warp so I think it's out of scope of your question.
So in our saga, the effect comes first (healing/teleportation/high support spell (generally it was my magus flying effect from his talisman which was a ReCo to fly 1000 persons at once [it's a result of experimentation, normally it would have been a teleportation spell for a group]) and the warp point after, but since it's 1 and no magus ever takes the character-killer (TM) twilight prone, there is no problem.
From what you wrote, it seems that in your Saga a Magus with Twilight Prone is forced to check for Twilight whenever he is exposed to 1 point Warping gains? Is that a correct assessment? That is indeed a Magus-killer, and not at all what the Flaw says, which is that Magi have to check for Twilight when they gain 1+ Warping points from their own botched magical activity, rather than 2+. Not whenever he gains 1 Warping from any source. The Flaw is not quite that severe!
(Please feel free to ignore my observation if it’s wildly off base)
You are totally right. I didn't even bother check the virtue once the alpha SG explained me the virtue, 10 years ago when I started playing.
Anyway, to be totally transparent: in our saga, botch dice start at 3 (not 1)*. When a player roll a 0, it's 3 dice + aura (even if magical, there is no "attunment" of magi to it... which is not RAW but a house rule) + additional dice if SG wants, so you understand why it's dangerous even with that correction.