When Giant Nixod was born, Ghost and Doll, who were chatting outside, became so scared of the beast that they immediately confessed their love for eachother. The spontaneous expression of similar emotions from both sides resulted in their linked genes to cross-connect via RNEP (random nixod electron pulse) which led to a fusion between the two. The resulting being is Leviathan, a creature so powerful they can barely be described as a Nixod, but more as a god. Though the fusion is temporary, if Leviathan ever reaches full fusion potential, they can destroy entire solar systems on a whim. Right now however, the fusion is new so they're still learning their moves and getting to know eachother desu.