"You will only get one chance to make it right. If you hesitate, it won't be undone."

He speaks with certainty though he doesn't know this man or his universe. He doesn't know about Thanos or the gauntlet in any specific way, but he knows a fair few things about magic. They're (nearly) universal, the rules he's sketching out for Tony now.

"Unfortunately, nothing can be done from here. This is an in-between place. Limbo."