O.K do to the extent and vastness of BGII I have many what ifs and questions.
For instance,
1. What if in the underdark you give the real eges to Phaleon?
2. What happens if in your dream with Imoen you attack her instead of Bhaal and kill her?
3. What the H**l am I supposed to do with all those items I'm getting quite a collection, Nebs head, Yoshimos heart, Lion skin, Human Skin, Head of a Wyvernn.
Anyone with any more What ifs? Post them here.

Hello Jon - my arch-enemy!! yeah, I got loads of what if too!!

What if you kill Bodhi after working for her?

What if you kill Renal Bloodscalp? Has anyone done this before? (when he is friendly)

What if you kill gaal by time stopping, and shooting a fireball into his group - before he starts even talking? will the high oisig man say "this must not come to pass.........."

What if Viconia is killed on the stake before she is even release?

heh heh can't think of anymore for now Jon. Gimme a break - I'll go have a shake and see what I come up with later!!

in order:
1. The matron dies , the demon tells Phaere who you really are and both turn on you. After killing the demon you can retrieve the real eggs.
2. You probably can't attack her/hurt her, but I didn't try. Why do you want to?
3. Neb's head take to the government building and give it to the Chief Inspector for a reward. The lion skin, once youv'e found the tanner is the killer, and Wyvern head sell, as I found no use for them. The human skin can be combined with the blood of the silver dragon and given to one of the merchants outside the pub in the Umar hills, once you buy a book off him, something about the Zhentarim. You also have to say his name which is coded on a piece of paper you get from the skinner quest in the bridge district( the merchant is the ring-leader). I have forgotten the name, but I gave it on an earlier post so try a search. He will combine the skin and blood to make some great armour, AC3, +4 to all saving throws and 20% magic resistance, which can be worn by any evil character only, of any class.

Yoshimo's heart has to be cleansed so he can rest in peace, for which you gain exp. I didn't have him in my party, but try the search as it has been answered before.

Take Yoshimos heart to any Ilmater temple, so that he can find redemption for being a traitor.

I couldn't bring myself to do kill Adalon, not even when playing an evil fellow.

Bodhi will not die before her prescribed time. I had prot from undead on in a previous battle and absolutely tonked her. For ages she was near death but the dialogue that involved her fleeing only kicked in when the scroll wore off.

If you get the real eggs from the demon it says they are 'tainted'. What happens if you take tainted (or any other) eggs to Adalon - she goes into a murderous frenzy right?

Nope, you can't kill Bodhi before chapter six.
If you even attack Renal, the invulnerable thief shows up with his supreme longsword and minces your entire party.
No idea about the third one.
If Viconia is killed on the stake... that's it. No Viconia for you.
By the time I got to Adalon I'd had it up to my neck with bloody dragons, so I didn't bother fighting her. As for retrieving her eggs, I tried scarpering from the Underdark with them, but they didn't sell for anything. : P

oh um what I did to that thief came to me in a flash of insparation. I took his sword loaded it in Infinity Engine and made it a normal sword! No more killing my whole party for him!

How can you create a sword and only YOU can use it Jon? How do you do a Blackrazor effect, on when you hit, you absorb blahblahblah... get it?

Well this wolf do things out of the blue sometimes...
Here are some, maybe spoilers for some, don´t know yet what I´ll write
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If you attack Imoen, she only dies and te dream sequence goes on, at least this happened to me, if you die fighting Bhaal, well first time I really died
If you kill Gaal and friends before you get the quest, a very annoyed Beholder will emerge and try to give you his very evilest eye he can... really bad cause you wont get the key to sewer passage and Ganx kangaxx alot axxx´s quest will be hard to deal with..
Viconia will burn if you et her stay at the pole and they ignite the firewood, logic?
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-Some of my own experiences, if you do alot of things out of the blue, most things will turn out for the better anyway, just be careful with who you kill...