(This FAQ was written by Jason.)
In Ascension, Melissan demonstrates using the power of Bhaal to resurrect various dead foes to fight against you once more. The Ascension endgame is a battle over those powers. So what, we thought, if the PC could turn the tables, and bring his own fallen allies to bear against her?
The exact mechanism has yet to be determined but will likely involve the opportunity to attempt to ally with a fallen friend after each "pool" fight. They will have minds of their own, however, and cannot be forced to fight. Some will fight willingly, some will demand the promise of resurrection, and others will simply refuse. Some of this will depend on the type of character you've played. Don't expect Ajantis to join a slobbering avatar of evil.
In general, the summon-able members will be those who were your party-mates in BG1, but there will be occasional exceptions.
Here's some actual Q&A:
Q: When will you be done?
A: Not sure, really. Depends on how fast we work.
Q: Won't this unbalance Ascension?
A: Probably not. Although we will give your allies weapons and abilities reasonably comparable to something approximating a TOB start character (why? because it's magic, that's why), they're not going to be Five/Melissan-level powerful. Turnabout is primarily a roleplaying exercise.
Q: Did you say that it was going to be the dead BG1 joinable NPCs available?
A: Yes, although not necessarily all of them. We'll work Yoshimo into the mix as well, along with quite likely the two mortal parental figures from your past, Gorion and Alianna.
Q: Will it be compatible with Redemption?
A: That's decidedly a maybe. Depends what the Redemption code is like and whether we'll be able to slot what we want to do around it.
Q: Can we have Tazok, Saemon, Rielev, Firkraag, Lt. Aegisfield, Gorch or the Umar Hills chickens available for summoning?