Universal Evolution: Heavens Trial

What's the strongest force that can drive someone to keep pushing himself\/herself beyond his\/her limits? Everyone has their own reasons but a being named Zykan was driven by revenge for him to seek strength after all the people in the place he lives, including his family were massacred by a beast not from Earth; leaving him the lone survivor. It was all because of a phenomenon where the Universe had udergone a big change called \