A magus was experimentating on a Perdo Vim spell (Unravelling The fabric of Corpus, level 50) to reach a major breakthrough (IE one of the parmulae in the bonisagus book). He succeeded in stabilizing at first attempt, and gained 7 warping points, who triggered a twilight episode; the comprehension roll succeeded by luck (12 vs ease factor 12) and the player rolled 6 with the simple die, gaining 13 warpings points.
I think such a twilight during experimentating is a good occasion to give him a major virtue (it happens rarely!). Now, I find myself hesitating.
The magus is a focused on Vim art, with all other forms at 5 and his techniques range from 12 to 24. He has already a major magical focus in magic (ie Vim magic with "spells" guidelines).
First, I thought about "Hermetic sorcery" because it's linked to Vim but after first thought, I think it would have needed the player to have at least 1 goetic art (which he doesn't have).
Mercurian magic isn't appropriate although the major benefit (half vis) is one of the magus reaching, since it would embarass the player with a downgrade in spontaneous magic (and the player uses many spontaneous MuVi 50 spells on his formulaics to emulate the "change totally a spell").
Twilight mastery would be a good one, but I always confound his effect (thinking it imposes 3 botches to trigger twilight in place of 2... but no: the player can choose effect of twilight). Besides, it's a special mystery ... not sure it's appropriate.
Maybe summoning or ablating? the PC being a magus with vim interest, one of the goetic arts (which uses, for magi Rego and Vim after an easy conversion - maybe 1 or 2 seasons of work for this labrat - or would you say it's freely done?) could be appropriate.
Have you other ideas?
Thanks for your insights (haha ), I need a breakthrough
Greater immunity - Corpus spells. Corpus spells apply only if he uses a special magic word to let them work (healings, longevity etc)
Greater purifying touch - blindness (not so useful)
Secondary insight - not fancy but useful
If he's that strong into spont, LLSM or Diedne. Consummate Talisman fits with MuVi. Or invent a virtue to allow formulaic MuVi on spont. Invisible to Magic and Vis Sensitivity fit the bill too, although it could be useless at his power.
I like Sir Swindle's suggestion and also the Greater Immunity to Corpus magic.
I had another wild thought: a version of Way of the Woods: Way of the Twilight Void.
Maybe a new innate ability (design using RoP:M maybe) to end magical corpus effects (anyone's, not just his), or disenchant corpus effects in devices.
A totally other direction might be the ability to 'dis'-animate the undead?
Which of the choices come up with so far would be coolest depends on the character. For something this 'big' I'd try to make sure that it not only made sense for the event, but for the desired direction for the character and his/her stories. It'd help if we had some idea of the character's background, personality, and goals/activities.
Thanks for all your replies. I chose to give him "twilight mastery" since this was his first major twilight and since he will be in twilight a lot more times in the future, with, I expect, many bad results. So far, I've taken note of your ideas (especially the Ways of Twilight) and the player has been sent on this thread to read your ideas .
That took no long for him to have a not understood twilight with 13 warpings points... He chose to lose a spell level 65 he had in 2 versions due to experimentation. Guess what?
), I need a breakthrough 
.