Now, yes. When Quendalon did it, House Merinita was much smaller; they may not have needed a focus on Faeries. On the other hand, I recall that Merinita was a very loose leader. Perhaps they just needed a focus.
A Tytalus could even be the good guy, standing alone at High Noon while lesser magi slink away.
That sure isn't any Flambeau...
grin Since Tytaluseses consider themselves "the best of magi," other magi are lesserers.
The Flambeau might be on the wrong side. Or he might withdraw from the fray because it is too squalid for him, or because he got tricked or trapped, perhaps by some point of honor.
As an addition to the question, "Can you change a house", can you be a member of more then one house? Some houses are "jealous", but several seem very open. Could you start as a Verditius, get Enigmatic Wisdom from Twilight, and so "join" Crimon and learn their Mysteries? Then get a fairy warping point and "join" Merinita, and learn their mysteries?
You either overestimate the lifespan of magi, or underestimate the amount of trust required for Mystery Cults (even Houses!) to be willing to Initiate people into their Inner Mysteries (and, subsequently, the amount of time it would take to earn enough trust).
And I think you'd have to leave the first Houses to move onto the next, and everybody from the first (and second) Houses would Wizard's War you into oblivion to keep you from sharing your secrets with people in the other Houses.
Theoretically, switching Houses is a thing that can be done. (Dual membership is questionable in all but the most extreme cases.) But between Mystery Cults? I can't see that being pulled off.
House Criamon would let you leave, although someone from the Path of Strife might turn up to have very pointed words with you.
Verditius would probably never let you leave them.
Bjornear and Merinita? I see both being persuadable, but only with great difficulty.
That's why I went the order I did. Some Houses are very jealous, yes. Crimon, Merinita? At least in canon, not at all. Both seem very relaxed (According to Houses of Hermes, Mystery Cults) about members. They seem to want Magi to know their "Mysteries", and for both houses, the entry requirements can happen by accident......
In an old and now long defunct Thebes saga I played a Jerbiton with an interest in building things. As he joined a cult teaching him Hermetic Arcitechture I realized using Verditius magic was a huge boon for this. So he found and buttered up a Verditius magus and once he was promised entry he renounced formally membership of house Jerbiton.
But this is - as are all Societates IMHO - an easy house to leave, seeing as it has no mysteries or deep secrets. True Lineages don't have house mysteries either, but they may have secrets or ethics resulting in the house being very annoyed if someone leaves on a whim. But they may kick people out. And I have great difficulties seeing a Mystery Cult house allowing a member to leave and possibly spill the secrets.
And I think renouncing your old house is a must when joining another one. Except for Tytalus as mentioned. But I expect that if a magus is publicly recognized as a member of Tytalus many houses would want him to either confirm or deny this, and act accordingly.
No, they wouldn't.
House Criamon's mysteries are self-occluding. If you don't believe what they do, you can't do what they do. The Path of Strife is an interesting twist on the mission, but it's still on mission. They don't need enforcers.
"Marius, how good to see you. Now, How do you feel about your membership in house Guernicus these days?"
"Master, I have always been a loyal member of house Guernicus! The Code of Hermes is my life! You know that! You instilled that into me when I was a child! I would and will fight and die for our house!"
"Ye-es, about that. I understand you're also a member of house Tytalus these days... I wonder..."
mmm-yeah. Not a nice scene.
Yes, Tytali can really be complete douchebags and just declare some magus a member of their house, just to stir things up. And they are really just helping said magus achieve greatness by offend him great challenges...
How is it being a douche when they are doing something to improve the life of another? 
@kingreaper: Bjornaer absolutely do not allow their initiated members to leave the House.
Verditius, I imagine, are probably the same way by necessity - busting the Verditius monopoly would bust the Verditius monopoly, plus they all have huge egos.
Merinitia is simply not organized enough to have a specific response to a Merinitia going orbus; they're like Ex Miscellanea in that they all more-or-less do their own thing, and I really don't think that their Outer Mystery is that big of a secret. Individual Mystery Cults within Merinitia might be more troublesome though.
Criamon don't mind, because their deep secrets are self-occluding anyway.
Also, Criamon have "guest" lineages who are Criamon by association rather than membership in the Cult (though they're welcome to learn the Criamon Mystery if they want) because the Criamon really aren't on board with having someone killed for not having a House. That said, Ex Miscellanea is the usual destination for Magi Orbi (and in some Tribunals, Orbi automatically join Ex Miscellanea.
Re: Tytalus: I assume that if a magus is declared Tytalus by their enemies, their own House will be pretty understanding. Guernicus in particular, because House Guernicus won't kick you out for anything less than abusing your Quaesitorial power for personal profit. It's mostly Tytali that you'll have to worry about, because now you're a beloved member of their House.
And yes, I have a concept for a "good Tytalus" who's currently awaiting a saga to play in, but it's worth noting that a "good Tytalus" would probably be unwilling to cooperate with at least some of the maxims of the House. For example, my concept (a theurge and Titanos who enjoys generally playing up the evil sorceress schtick, who has nothing but contempt for the Divine and tends to invoke Prometheus and Hekate, but who is incredibly compassionate and defensive of the weak and helpless because she chooses to be so) has no use for the Book of Instruction unless she's getting off the chamberpot.
The Book of Instruction is allegorical. Every master uses the book of instruction, not just Tytalus masters, though they may not know it.
The biggest thing that bugs me about House Tytalus, is the veneration of Tytalus above everyone. Doesn't fit within the paradigm of being the best version of yourself, striving to overcome all one's challenges. Tytalus is a good example, but the journey is intensely personal, and Tytalus should be well aware of this difference.
You are both on my list!!!
And even if you could, why would they bother, unless your inapt actions were causing severe problems (beyond the typical inapt actions of other magi, nobles, etc)? Someone from the House might be interested in watching, just in case you were groping your way along a new path or something?
In general, if a Mystery intitiation involves a vow or personality trait or some other kind of commitment, I see that commitment as being part of what allows the mystery to work. Breaking that link damages the conduit to power, insight and revelation. An initiate doesn't learn a mystery virtue; he is changed.
Anyway,
Ken
How... apt.