Galactus? The tarrasque. It appears every now and again, following it’s heralds (spoilt for choice here!) and all the worlds mightiest adventurers must band together to defeat it.
In fact, theres one of the biggest changes to my Marvel/DnD world. The reason for adventuring. It’s not about gold or magic items, or personal power, it’s now (even more) about heroism. If I design my world along Stan Lees lines then all of a sudden it becomes about a war between the alignments. That’s pretty cool actually. The villains are the big monsters, but they only have lairs, not dungeons, and they don’t just sit there waiting, they have schemes, of world domination. That’s where the adventurers come in. They react.
Dr Doom? A war forged wizard, with his own country at his beck and call. A tortured genius of course, and intrinsically linked to the worlds greatest family of adventurers, the FF.
The negative zone? Astral Sea.
Yeah. This is going to work.