Inside tree stump in A4.
Form of payment.
+1 for looking into the stump, +3 for taking pouch, +3 for opening pouch, -3 for giving pouch away.
Get close to the tree stump and look inside (circled in image to left). Then, use an action to retrieve the pouch. After that, view the pouch to find that it is, in fact, filled with Diamonds.
The pouch of diamonds are not needed to complete game, but are worth points.