Okay, this is weird. I did the Schuylers thing with Virgil and Sogg. I killed everybody (and every...thing...in the place) and then left. Later Virgil got killed so I picked up Magnus as a follower, and then Dog. For grins I decided to take Magnus on a tour of the Schulyer establishment, since he was so curious about them. We went down to the bottom, where I used a Conjure Spirit or whatever it is called to call up the spirit of Pelonius Schuyler, but the ghost wouldn't talk. Magnus made his usual comments on the way down about a travesty, etc. and I reassured him I would fight by his side. Of course there was no fighting since everything had already been cleaned out. Well, on our way back up, he stopped me to thank me for "fighting by his side." In response I said it was time to go our separate ways, since I planned to get another follower to take his place elsewhere. This ended the dialog and Magnus was no longer in my party. Instantly, the "Quench Life" animation appeared, and Sogg, myself and Dog were all instantly killed. What the heck was that?! On a separate note, wandering Tarant at night I saw some orcs run into Stanton Importers and start a fight with Stanton and his guards. I had never seen two forces go at it before in this game (happens all the time in the Fallout games) without me being involved, so I was intrigued enough to experiment by either intervening or not intervening (restoring saves - every time I walked by that place, it would suddenly get attacked by orcs). Well, it didn't matter whether I intervened or not - Stanton was indifferent to me regardless and would only say "Well, it's the new owner of the mine!" Not sure what is going on with these orcs or what quest they are related to. I have never seen creatures in the game just attacking each other while I watch before.
It seems that there is some kind of curse in the Schuylers' catacombs, that is activated whenever you somehow "mistreat" Magnus- reject him as a follower or try to take his glove or his book. Just dump the fellow OUTSIDE if you don't need him, and if you want his stuff, also wait till you're out.