Shadowhunters may not be returning for a fourth season (despite fans' best efforts), but that doesn't mean some of the planned Season 4 storylines will remain under wraps.

Showrunners Todd Slavkin and Darren Swimmer told TV Guide that one of the challenges of sitting down to write this two-and-a-half hour series finale after getting the sudden cancellation news was deciding which storylines to wrap up and how to do that while incorporating condensed versions of story arc they'd started mapping out for Season 4.

"Our immediate feeling was that it was incredibly daunting, and it was almost an impossible task," Swimmer said of writing this epic series finale. "But we already had an overall idea of what Season 4 would be. A lot of what we see in the episode turned out to be condensed versions of what would have taken several episodes in whatever we projected Season 4 to have been. So that was kind of our launching off point."

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"We got some of the writers together, so we had a mini-writing staff," Slavkin added, "and it was super exciting to plan because we're fans of the show — what would we want to see? How do we want these people to end up? How are we going to feel at the end? We're positive people... we love pushing off the show and examining everyone so that the fanfiction writers could just go crazy after it's over. Those stories all continue in each of their own ways."

Every rose has its thorn, though, and in Shadowhunters' case, that thorn is the annoying spoilers from the series finale that have made their way onto the internet since the episode was filmed last summer. Regardless, Swimmer and Slavkin say that there are still plenty of tricks up their sleeves in this finale, so if you think you know where it's all going, guess again!

"It's unfortunate that things were spoiled, but not everything was spoiled and there's a lot of shocks, surprises and thrills a long the way," said Swimmer.

Shadowhunters' series finale airs Monday, May 6 at 8/7c on Freeform.

Katherine McNamara, <em>Shadowhunters</em>Katherine McNamara, Shadowhunters