Answer:
He stands beside the road. In a purple cap at tattered green cloak. Those who touch him, curse him.
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.
Three little letters. A paradox to some. The worse that it is, the better it becomes.
When it comes in, From sea to shore, Twenty paces you'll see, No less, no more.
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.