Board Thread:Questions and Answers/@comment-28898329-20160901162911/@comment-32182236-20200129182646

Generally a lot of it relies on headcanon without explaining how they know that is the case. For one, Chara wouldn't know what Asriels attacks are. This is a new form and he's never taken it before. Yet this is explained away by saying this is a character he invented as a child, even though there's no indictation he ever did so (plus "god of hyper-death" is specific to this situation).

Asriel was the ONLY one with attacks the narrator knows. And the narrator gets the flavor of Monster Candy wrong sometimes. They're not omniscient. So they have to be someone who would know who Asriel's attacks are. While not being omniscient.

Chara's just the best fit here. And really, God-Of-Hyperdeath seems a bit.. cheesy.

Then again, it could just be that the Dreemurrs are bad at naming things. That's what the rest of the evidence for the narrator theory is for.