It's an X-Men event, basically a cross between a state dinner and the Met Gala where a bunch of characters from across the Marvel Universe has been invited. My assumption was that it's Magneto, since the solicit makes it sound like Doom is staying on the Krakoa-owned Mykines (where the gala is being held) a little longer and I can't think of many other Krakoans who'd be considered "old friends" of his, except for maybe Emma--but I'm leaning towards Magneto since he's part of SWORD's cast.