How can I reverse spell mutations?

Hint 1 of 8:

You only need to reverse one mutation.  You can use RATANT to un-RATANT all
but one spell.

Hint 2 of 8:

There's no way to RATANT RATTAN, since you can only have one of those two
spells at the same time.  You need another way to mutate RATTAN back.

Hint 3 of 8:

Have you been to the Sorcerers' Guild in the light house?

Hint 4 of 8:

One of the sorcerers there might be able to give you an answer.

Hint 5 of 8:

A treatise will appear at some point when you're in the Guild.

Hint 6 of 8:

The pimento moss can be found in the cannon at the fort.