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.
An ancient, psuedo-immortal race has been manipulating something important (politics, religion, economics, etc.) for centuries. Hardly anyone is aware of them, let alone their goals.
By late afternoon, the sky starts to cloud over. The sun shines behind the fluffy clouds, gilding the edges and showing a Jacob's-ladder of rays streaming through the gaps...very pretty. Gradually the clouds shift into a new configuration: you realize with awe-struck, preternatural clarity that the clouds form a map of a coast-line that you know against the blue sky as ocean: surely it's a Sign! Suddenly, the golden beams coalesce into one long ray that strikes across the blue. A star-like gleam flashes under the ray: perhaps it is an island? But the charts show no island there...who would want to hide an island? Who could do it?