Hostile Plasma Alien

In the center of the earth were was a secret chamber. Not one with a door. One that you couldn't open without love, you couldn't see without courage, and that you couldn't touch without imagination. In that chamber there was a very small ball of pure darkness, pure hatred, pure evil. A wise man wanted to nurture this darkness and turn it light. Being nothing but kind his hole life this was just natural. But, the darkness consumed him and took his form. His soul. And a small blue dot appeared on the things chest. A small beam of light. The monster grew from the small orb to a terrible being. Made up of souls that were not his. This monster gave itself a name: Ontinerst (On-Tinn-earn-ist )
Ontinerst was very good at charming beings. He shapeshifter into whatever being he had to. He worked his way up in the galactic government. Until he was the vice president on the universe.
Only 2 children knew about his secret. They were children. What chance did they have at stopping him and his plan on stealing the soul of the president...