He is a young boy created from dark matter
STORYEditGrey was created when the overlord was destroyed. It took a pile of dark matter before it died. After the ninjas left the island Grey was stranded and lost. But after 2 months he finallly got off the island. Every night Grey is controlled by his darkness and runs everywhere creating chaos in Ninjago without him even knowing it. After 4 months of his out of controll actions he arrived at the bounty as if it was destiny. Sensei noticed his arrival using his spirit smoke. Sensei had a terrible vision of him destroying the bounty, but he invited him in anyway.
Gray wears a black kimono with a mysterious symbol on its side and back. He has purple hair and grey pants. His armor on his shoulders are also black. He also has a purple belt.