SPOILER#2

Noah is a sinner who mimics human form in order to get to Allen (especially the eyes).

His goal is to get Allen to the hell where he lives, and Allen's fate depends on his mood.

He somehow made Campanella a villain when Allen was still in this world and made Allen come to CORE. (I can't go into details, but I heard he made him say terrible things.)

How did he find Allen?

Noah found Allen when he was still alive (when he was human). At that time Allen was still a child.... (By the way, what he looked like then and what he looks like now are very different)

*Supplementary information Noah doesn't mean that he loves Allen. He just doesn't want to give up his perfect “ artifact.”