I am royalty upon ice, yet my kingdom melts in summer. What am I?

Tell me, How does the ocean greet the shoreline?

I wear a suit of gold and red, With brilliant thoughts inside my head. I snapped my fingers, saved the day, And turned the darkest threat away.

If athletes get athlete’s foot, what do elves get?

As I am, a green symbol of vitality and endurance But swap my second and third, then spell me in reverse and my meaning changes to make something weaker