Klein, the Moonlight's Threat is a custom champion in League of Legends.
This concept and, most importantly, his character, are a champion born out of "Areneth", a story of a wolf pack from the author "Gabriela Martinez Garcia" (Spanish).
Klein's abilities have no cost. His secondary resource bar instead displays his Fury. Klein starts the game with 0 Fury and can have a maximum of 100. Klein will generate 5 Fury whenever he hits an enemy with a basic attack and 10 Fury (+ 2.5 for every enemy hit beyond the first). Fury does not decay idly.
Fury is only needed as a requirement for the use of his ultimate True Howl, which allows him to change form if he has 100 Fury. Klein won't generate Fury unless he has at least one point in True Howl, and once he puts the first point on the skill he will gain 100 Fury immediately. Any gained Fury cannot be lost except by depletion of casting True Howl.