(SPOILER)Umm actually Zemus was mentioned in the game before you fought him. It was more of a outright saying he esxsisted as opposed to Necron who was onyl foreshadowed to. FuSoYa mentioned Zemus and ecxplained him long before you actually fought him. It was also foreshadowed of someone controling Golbez back when Tellah used Meteo. Necron was only indirectly mentioned by Dr. Tot and I beleive Beatrix.