Previously, Grieve had only existed within Tess, being expressed at her darkest of moments, however, upon the crash, they somehow managed to separate and become individual entities. Grieve then became the host of the Radioactive tournament, to try and kill off video game characters, only to be stopped by Tess.
Grieve wears a toxic mask to cover his face from others, the only thing showing through is his orange eyes. He also wears a black cloak, with a hood over his head. The lower half seems to have cracks in it, where radioactive-looking ooze appears to glow through.
Grieve is evil and wicked, solely wanting to cause chaos and destruction. He doesn't have a care in the world, all he wants to do is bring down Tess in every way possible, and make her suffer.
Grieve has the power to manipulate darkness, and he also has a lot of expertise in creating weapons and bombs.
Grieve appeared in Tiffany's dream, startling her. She doesn't know who he is, or what his purpose is, raising more questions for Tiffany.
To be added.