You don't need to go there I don't think. If you do, just go through the
fire field. If you can't dispel it, then it's probably just an illustion.
That's not correct. On the Isle of Ambrosia there is a negate magic spell in effect
for most of the day (you can see the twinkling in the air).
The easiest way to cast your spells is to jump on your transport (ship or carpet),
and sail away until the spell stops (ie you can't see the twinkles anymore).
Then you cast a change weather spell (because while it's raining, the negate magic
spell won't restart). Of course rain doesn't last very long, so you high tail
it back to Ambrosia as fast as you can, and cast what spells you like before the
rain stops and the negate magic starts.
It's a round about way of doing it, but it beats waiting all day for the brief
period during which the spell breaks (I never figured out what time of day that
was??)
Hope this helps.
David.