Summon Spell

Hint 1 of 4:

You will find one in the Draracle's Museum.

Hint 2 of 4:

It's just next to the entrance.

Hint 3 of 4:

Take the skeleton key.   Doing so will open a wall behind the orb that
introduces you to the museum.  You'll find the summon spell behind there.

Hint 4 of 4:

There is also a summon scroll on level 3 of the Huline Jungle.  It's just
beyond a waterfall.