IF it's the same as the last event like this, by upgrading to level 5 you win the Scroll which is the prize for the event. There will most likely then be an UNTIMED portion of goals to follow which allow you to choose which animal you want to craft.
I'm not saying that is exactly how this particular event work, but last time there was so much confusion about exactly what we were playing for. It is a reasonable assumption to make that this will be the same as last time, which was the Fire & Ice Dragons. It is definite the prize is the Scroll - the screen shot (which was posted by S8 Regina) says it.