Zadga is part of a team of spatial-law enforcements called the Sidewinders. Not much is known about him, but due his appearance is rumored that he is from the same planet as The Stranger. But even with all the secrets around Zagda his motives on joining Ophidian Games are very clear, as he wants to capture or kill The Stranger.
And as The Stranger he also has a great control over minds and is willing to use it to achieve his propose.