It's the best

Whilst frolicking through the picturesque scene, you notice something strange up ahead. A massive stone doorway, just sitting in the middle of the field, its rustic wooden doors securely locked with a giant golden bar. Across the bar are a number of polymorph-shaped slots, you count... 17 of them.

That's a ... weird number. You count again- 123456789... yeah, yeah, that's 17. Okay.

Well anyway there's 17 of them.

What... whatcha gonna do about this here door thing?