That's right: From June 3 to July 2, there'll be a post each day highlighting Teenage Mutant Ninja Turtles canon immigrants. Now, because TMNT canon is a little confusing, it can be hard to tell what counts as a canon immigrant and what doesn't. So for the purposes of this blog, a TMNT canon immigrant is anything (a) from the movies, cartoons, video games, toy lines, or tie-in comic series that later appeared in (b) TMNT volumes 1, 2, or 4 [because they're by the original creators] or TMNT volume 5 [because the original creators are involved, it's the new official continuity, and its goal is to use as much of the diverse TMNT lore as possible].
Darius Dun was essentially the Ninja Turtles version of Lex Luthor; while the public saw him as the upstanding head of a major company, he actually used that company for various nefarious means. Unlike Luthor, however, he lived in the next century. Dun first appeared in the Fast Forward episode "Obsolete" (August 2006).
In the IDW world, Dun plays much the same role, only he's in the present and he's working with the Street Phantoms. He first appeared in Teenage Mutant Ninja Turtles #51 (October 2015).