Answer:
An iron horse with a flaxen tail. The faster the horse runs, the shorter his tail becomes.
Twigs and spheres and poles and plates. Join and bind to reason make.
A precious stone, as clear as diamond. Seek it out whilst the sun's near the horizon. Though you can walk on water with its power, Try to keep it, and it'll vanish within an hour.
What goes up but never comes down?
It is weightless, you can see it. If you put it in a barrel it will make it lighter?
Special abilities and brightly colored underwear are all you need to be one of these.