My party decided to befriend Filge and take him along to explore the Ebon Triad. In WC, it states that if this option is taken, Filge "betrays them at a key moment" yet to be described in the 3FoE issue. I have looked all over (I think) in the 3FoE, but cannot determine when Filge stabs them in the back.
Meanwhile, the PCs just cleared the Temple of Hextor, and I have a probationary player playing Filge. I need to prompt him as to when Filge stabs his "buddies" and runs, but I can't seem to find it.
And suggestions?
Abstain, especially if Filge is played as a PC.
There is no real reason for Filge to literally "backstab" the other PCs as they explore the temple of Hextor, or any other part of Dourstone mine. Remember that he is not in league with the Ebon Triad, but works for Belabar. He has common goals with your party here.
On the other hand, he can act inside as Belabar proxy to destroy on the sly any evidence implicating his boss, and once outside, go NPC and run to Belabar to let him grab a political advantage from the players' work (by being the first to tell the mayor about the cultists, and how HE worked with adventurers to advert the dire threat, for example. After all, there will be a ownerless mine to grant to somebody, very soon: better to get an headstart).
So, Filge does "backstab" them in a non literal way, your players get a free lesson about the perils of trusting strangers, even ones played by other players, and it's the perfect time for your probationary player to upgrade and get his own PC.