Death and Resurrection
Life is commonly difficult, especially for those who choose a life of hardship and adventurous excitement. The cycle of life is never ending and continues its birth, life, death cycle for everyone. With divine aid and assistance, however, at times it can extend this cycle greatly, even halting it for a time. Death is different among nearly all game settings. Please read this with the understanding that it may not fit your particular game setting and style, but is an alternative.
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.