Team Awesome main evil character.
Alone he is capable of turning entire lands into ash wastelands.
"I am the end of all things" as he like to say. Here watch this to hear his voice [link]
This voice is changed into this dark reaper like voice by his HELMET. This helmet is actually a very powerful Artifact, that is capable of doubling his magic powers. But it also looks cool and covers his ugly face, so he can be... accepted by children.
Here have a part of his Back-Story that lead to his madness. Listen while reading [link]
He came to the planet with his sister in order to restore it to its former glory. They wanted to make this world beautiful again. And yes he used to be a good character, Light's brother, a Prime Alicorn with powers of creation. He commanded the might of all Elements ( fire, water, air and earth) AND was the master of Night.
After many years of repairing the planet, adding new life forms ( ponies included) Light proposed that they tried to create A VERY powerful stones in order to make the world recreate itself without Light and Dark help. Light created Elements of Harmony, while Dark Elements of Nature. Light was successful with her elements, but Dark... Unfortunately his Elements fused with one another. That lead to creation of wild, uncontrolled Elemental Lord. Dark stopped him by using his sister elements.
Now the important part.
Dark used Elements of Harmony ( ALL OF THEM AT ONCE) and used this power to take the Elemental Lord into the planet's core, and THERE he took away Lord power, and left his corpse in the core.
When this power return to Dark... something unpleasant happens. Dark had all the energy of Elements of Harmony in him, and now THIS additional power came back creating a mixture that twisted him entirely. His body, mind, powers, personality EVERYTHING became twisted version of his former self. HE BECAME OVER SATURATED
Every single emotion he felt from this point was twisted, over saturated.