In the meantime, Thor has taken himself to London. With the help of his old friend Erik Selvig—the astrophysicist from the first Avengers movie, Thor locates “The Water of Sight.” Imagine a big, dark puddle, only hidden underground and way more mysterious than your average puddle.
It turns out that this water acts as a kind of portal. Thor dives in in order to re-visit the hallucination-dream he experienced when Wanda Maximoff first hexed him.
The dip pays off (unlike most forays into hidden, underground pools of murky water). In the resulting vision, Thor sees that something was hidden inside Loki’s scepter. It’s a kind of jewel, exactly the same magic gem that Ultron is, at that very moment, installing in his new vibranium body.