Zagreus actually feels a little superfluous and he does have a priestess to whine at. "So are you two going to fight or talk or-"
"You're my grandson," Demeter interrupts.
He falters. There doesn't seem to be any follow up so he offers, "Uh, yeah? I mean, you must have wondered how I was able to break through your curse, and, well, you freeze the earth in my mother's name."
As her mother, Demeter is entitled to her revenge. As her son, Zagreus is exempt from that rage by custom and blood. He's son of the goddess of spring and the god of life and blood, and he wouldn't have been able to do nearly as much without that, but this is the real trick up his sleeve. It's allowed him to chip away at Demeter's endless winter while the other gods failed one by one, all the way up to Zeus.
Demeter's eyes narrow then she focuses on Persephone once more. "You really hate me so much that you'd choose the god of the dead over your own mother? Over the suitors I'd picked for you?"
"You made me choose," Persephone snaps. "I hid myself from you because you wouldn't accept what I wanted."
"Selfish," Demeter hisses, the wind picking up around her. "Ungrateful. Arrogant. Foolish."
"Controlling," his mother returns furiously. The earth trembles beneath her feet. "Ignorant. Pompous. Blind."
"Okay!" he says, looking between them. "Maybe we should-"
"Go to your temple, Zagreus," Persephone orders. "Your grandmother and I have some things to discuss."
They're going to try and tear each other's throats out. His orchard is going to take so much damage. "Well, uh, shout if you need me?"
Neither of them acknowledge him.
Zagreus finds Eliana anxiously pacing in the main hall. "Prince! Are you - I apologize for," she trails off, looking him over, then frowns. "What's wrong?"
He opens his mouth, closes it, then says, "I think I just got sent to my room."
Eliana blinks and then her lips twitch and she's turning her back on him to muffle her laughter. He grabs her by the shoulders and rubs his knuckles into the top of her head in retribution, but that just makes her laugh harder.