Shattered Island has three elemental gates, one for each starter figure. The magic gate is found after pushing two turtles to reach the jump pads. BEFORE going to the pads, push the second turtle to the left until it forms a bridge to an island on the left. Go to that island and use Spyro to open the magic gate. It leads to a hat and a soul gem.
You'll also see tech and water gates before climbing the ramp to the trapped royal family. They can be opened by Trigger Happy and Gill Grunt, respectively.