"How can you not have been born? You're standing right there." He's not upset about it, just curious. If he understood, Nico would have to agree with his life being impossibly strange. "The Fates are annoying like that. It wouldn't be so bad if they weren't so mysterious about everything. I think they like making people squirm."

He assumes they're talking about the three Fates, at any rate. Hard to say, because he has no idea what the Speed Force is. "I ... don't know what that is. I do know that mortals see what they expected to see in the Underworld. If you expected the Speed Force, that's what you got."