I'm looking for a fantasy novel, pre-2000. It's young adult fantasy.

* Magical abilities involved talents similar to psychic abilities.
* One character could hide the group, preventing others from seeing them.
* One character could start fires.
* They were on some sort of quest and had to go into the enemy territory.

Argh! It's so frustrating. I can't remember much about the book, but would recognise it instantly.

It's not Xanth and not Julian May. It's sort of a Stephen King's *Firestarter* meets Andre Norton type novel.