Playing ToTSC. Just returned from island and now face Mendas. Can't seem to get past him though with Mendas duplicating himself. Any strategy on how to beat these odds?

Cast every protective spell you've got on yourself first (before going in).
Then try some domination/hold person/dire charm spells on the extra wolvere(s).
You should get at least one on your side for a while.
That should help you out a bit. Summoned monsters can be helpful too. (If only for cannon fodder).

Hey, speaking of TotSC, did anyone ever beat Shandalar? I tried to take him out numerous times, but he kept dimension dooring away and I could never find a way to kill him fast enough. Anyone ever accomplish this feat. Sorry to get off topic, but the topic reminded me of this question.

The same questions popped up a year ago or so and it was determined back then that he's unkillable, same as Elminster.

you can kill Shandalar, with a mage/thief or an invicebelety spell and magic missles, Aproach him invicebel and cast a magic missle then run away and go invicebel again and attack him again with magic missle, you might need to rest sometimes but he's worth it- Robe of neutral archmagi, potions,lvl. 4 and 5 spells and more exp. that you get for killing Drizzt!

Anyone who manages that, send me a screenshot of it.

I'll send you one this month!

I positioned my party in a circle around him but far enough away so his fireballs did not reach them.
I let Jaheira charm some commoners which I sended to attack Shandalar. While he's busy with them I equipped 4 party members with a wand of magic missiles. I found out they did most damage (most of the time 5 HP) per shot and they are quick so they disrupt his spellcasting. My mage Dynaheir was constantly casting dispel magic.
That way he goes down rather quickly. I found out that you have to time the first dispel magic spell very well so it hits just after Shandalar's globe of invulnerability goes in effect.