When you meet the old priest with the
funny green hat (he's usually outside his hut), offer him one of your
magic spells. When he chooses the spell he wants then cast that spell.
During the spell casting animation press Esc and you will bypass the
animation. This makes the old man ask "Where's the spell son?" Now
choose the 'Help" response. This will make the old man go back into his
hut. When he returns he will give you one of the hidden secrets. Repeat
this until you have unlocked all the secrets. There are 20 in all.