Sans has been holding back mostly, since the ritual has started to be put together - he's watching the craftsmanship behind it curiously, but his goal is to defend. Then, of course, the crow sisters are abruptly put down, the True Fae show up, and Psi decides to take the stage.

This seems like a bad thing. The lasers don't strike him as any surprise, anymore, but who he's aiming them at? This seems like a bad, bad idea.

His sockets go wide, and his flies up to meet Psi in the air, but he can't bring himself to act. He's paralyzed, for the moment, unsure of what to do.

"Psi! Stop!" he shouts after him. "Dude, back it off!"