Between Cross Unity's seasons 3 and 4, Necron and Renie, which were interacting ever since after S2's ending, decided to fuse in order to fulfill each other's deepest desires. For Renie, this was pure freedom order to make the new Omniverse as his playground. For Necron, it was power like never before ( maybe comparable only to his Death Horseman form, but that really depends ) This new form ( which is named Necrenie as a placeholder ) posseses as much power if not more than both Renie and Necron combined, which is a lot. In terms of personality, he posseses both Renie and Necron's main features, making deadly games in order to please himself. The background is his own personal realm, similar to how Renie had his own inside the now useless lamp.
The model is mine @anexus for Cross Unity. Music is mr capgras encounters a secondhand vanity by Will Wood.