Simon “Wonder Man” Williams shows up and attacks the team, in a moment foreshadowed in the previous issue. He knocks out Thor, beats down Wolverine, and then gets knocked away by Protector (Noh-Varr). Before he can attack again something happens and he’s gone without a trace.
He just kept saying that he told Steve not to do it, and that he tried to warn him. He doesn’t make a lot of sense, but I think it’s intentional.