Find a prism spell.

There is a lizard-sized path a bit to the north of the entrance to the ruins
from the Savage Jungle, in an area where there are a lot of holes and pits in
the floors.

If you take this path, it will lead to an area containing a few prism spells.

To get out of the area, head to the west and look for a door.  If you open
the door as you're standing to its west, you will be able to jump over one of
the pits and back into the rest of the ruins.  (If you stand to the east of
the door as you open it, it will swing toward you, so you can't get past it.)