Curse those greedy delvers! But what with? I know! How about Aurophobia, fear of gold? Or Barophobia, fear of gravity? And I can hit that annoying wizard with Bibliophobia, no more spells for him!
The TRUE origins of Magic, and dont even get me started on Prophecy.
If a creature is transformed into another creature (say, a human into a dog), then that creature will become more and more accustomed to the new form until a point is reached where reversing the spell is impossible. A second transformation is possible, but the creature will have to go through the whole process again.