The Blacklist's top 5 villains are not set in stone.

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Red's (James Spader) criminal hit list is ever evolving, but no matter how many despicable and slippery characters the Mr. Reddington runs into, the ultimate number of baddies will be dictated by the length of The Blacklist's run.

"To be quite candid - Spader said this once - there are as many Blacklisters as there are episodes that NBC will let us do. There's no hidden algorithm or method to the Blacklist numbering. But, they are sort of weighted," series creator Jon Bokenkamp teased, according to The Wall Street Journal. "We do think a bit about it and wonder, 'Where does this guy fit? How would Red rank him?' So that's how we come up with the numbers."

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So far the highest ranked blacklister we've seen was Tom Keen, and it seems the Top 5 will remain under wraps for quite some time.

"I know a few who, in the mythology of the show, will end up in the top 5," Bokenkamp said, carefully sidestepping the question.

Who do you think are in the Top 5? Have we even heard of them yet? Sound off in the comments below!

The Blacklist airs Thursdays at 9 p.m. ET on NBC. Click the video below to see a preview for the series' next episode, "Quon Zhang."