I was just reading over Philippus Niger again (GotF, p. 59-60) and noticed his spell Dreadful Bane of the Fae.
Appearantly it works like Demon's Eternal Oblivion, but against Faerie Might.
Yeah, it's a might stripper.
Now, we know that might strippers reduce the might score and so destroy the Vis that would be left over in the corpse.
But what if the target is a fae, with External Vis virtue (RoP: F, p. 50)?
The Vis might well not even be in range of the magus when the DBotF is cast!
I can think of three possibilities to play with:
(Of course there's a fourth possibility - the faerie's might is stripped and the faerie can be killed that way, but the Vis is unharmed. But I don't like that one.)
I thought this was not an absolute, but only one possible interpretation. Is this described somewhere as "the way it works"?
Stands to reason that reducing the might would reduce the vis, I agree with this approach - at the very least a great reduction in vis.
I was sure I'd seen it in one of the RoP tome, but now that you're asking... Nobles Parma?
I have never seen or even heard of this interpretation before.
RoP: I, p. 33.
It is also the premiss of this spell.
Admittedly, this only indicates that might strippers have this effect against demons but we have used in more generally.
Right - so long as we are talking only about demons. But demon corpses are "destroyed" when stripped of all MM by PeVi, and so the loss of vis with the loss of that corpse makes some sense, which may or may not be the same with creatures of other Realms.
Not that that isn't a perfectly reasonable houserule extrapolation of that rule*, but it's not canon outside of "demons".
(* There are many other perfectly reasonable houserule approaches, and not all creatures/Realms have to work like demons do or the same as each other. For instance, some, when stripped of all MM by PeVi, might......not die but the vis is destroyed
...not die, but the vis has been reduced.
...not die, and the vis is intact.
...die, but the corpse remains.
...destroy the corpse, but (somehow) the vis remains (for instance, a Fire Elemental that leaves a cinder of Ignem vis, etc)
...banishes to their Realm, with or without (all) their vis.
Then there is the question of whether every/any creature of the Infernal realm works the same as "a demon" - infernal skeletons or zombies, an Infernal ghost*, a literal hound of Hell, etc. etc. If an earthly corpse is animated by Infernal forces (and somehow imbued with vis), then why should it disappear, and then why should the vis be lost? Iirc, there is text that implies that they are, in fact, all one and the same nature, "Infernal", but it's not spelled out in so many words.)
(* Some rare ghosts, when destroyed/dispelled/put to rest, leave an earthly token of their passing (often floating to earth from their last location) - and that can be imbued with vis.)
With or without that virtue, there is no rule that specifies that vis is destroyed in Fae creatures. Especially since it's unclear if stripping a Fae of MM destroys that corpse.
SG's/Troupes should decide which (single or several) of the above suggestions is most appropriate in any one case (they don't all have to be the same, but could be), and apply as desired.
(As a SG, I like creatures, especially fae, to be unpredictable in every way - keeps Players on their toes, and keeps possibilities open.)
Just to help confuse things, let me point out the Bind Magical Creature inner Mystery of House Verditius, HoH: MC, page 134. Might sucked from a Magic creature to empower an enchanted device strips the creature of Might but does not kill the creature. Nor does it destroy the vis. While this doesn't address the original poster's question per se, it adds another element to the already muddy waters.