Lightning resistance is low - quite handy for a mage.
Warrior: keep clear of her, so she can't blow her kiss of death,
use ranged weapons
Drink purple potions to boost up your resistances - if you're in trouble, run back to Zandalor, he can still heal you -
or drink mana/health from the shrines there, they fill up.
Use Banish to get rid of her knight
take a shadow potion, you turn invisible then use the special warrior whirl attack not on but near her. You remain invisible and she shouldn't respond
can you blind here? Then she's helpless and then bash her.
Mummies are easy: Low fire resistance.
Lockmar says this:
IIRC, the succubus usually starts with a physical attack first before casting any spells. She is also pretty fast. Create distance with a limbs of lead spell. An effective limbs of lead spell will be at around 4th level. Unlike many other spells, it can't be resisted. Then start shooting arrows. When the limbs of lead spell wears off, cast it again and shoot arrows. Keep on repeating this sequence of attack. You can also try casting skeletal wall first and then shooting arrows but if you do that she will start using spells. Be careful of the knight that she summons and of course, as Kiya mentioned, her kiss of death.