Aficionado ears may prick up at the mention of Elder, since he has a dubious alter ego as the Mole Man – the Fantastic Four's first adversary in issue #1 of the comic. In the source, he's a scientist who discovers a hitherto unknown subterranean kingdom after being stranded following a hapless expedition to Monster Island. When nobody believes him, he decides to stay in the aptly named Subterranea as its first ruler, and show the surface world what it gets for not taking him seriously.
Film wise though, the Mole Man half of Elder's personality is set for another outing. We're told that for the time being Nelson will appear as a scientist only, leaving the potential for villainy in future instalments. Nelson has been here before, playing Samuel Stern in The Incredible Hulk (2008), who last time we saw him was well on his way to becoming evil super boffin The Leader. Since Hulk has not yet earned any further solo sequels, Nelson must have his fingers crossed that jumping ship to 20th Century Fox will allow him to go the distance this time.
The studio currently has the Fantastic Four sequel slated for 14 July 2017, so maybe that's when Mole Man will emerge. But first there's the small matter of getting the new first Fantastic Four shot and released. It's still officially in pre-production, but should be underway shortly, ready for its release date of 18 June next year.