Custom Characters lvl 54 (Villains) (?)

ok i have been trying to make mission with villains that are 54 in level. I see many and they are custom characters, but rikti for example, Comm Off of Rikti to be exact and they say the missions is 54-54? How is this done? How do i make a custom villain level 50 always?
I figured out how to make custom charaters (villains) from the original in the game, just cant get them 50 or 50+

Put one of the heavies from Recluse's Victory as a captive somewhere. They're level 54 only and will limit the mission range accordingly.