Evolving Mega Sceptile costs 200 Mega Energy the first time, and 40 Mega Energy every other time.
Standard game images
There is a very low chance that you can get a shiny Sceptile, which has the following appearance:
About
"The leaves growing on Sceptile's body are very sharp edged. This Pokémon is very agile—it leaps all over the branches of trees and jumps on its foe from above or behind."
