They mentally run that sentence back and replay it to make sure they heard correctly. They did, and the human seems very certain that this is a wizard-related situation; this is an established feature of her worldview, not a wild guess after exhausting all other possibilities.

// How do you know? they ask with a nervous whistle. If she's even partially right, that means they're in a situation most closely comparable to the teleportation accident that separated Tracer from conventional spacetime. Without Ganymede.

// I go by Bastion, or E54, they add when Ylva introduces herself.