Though even The Doctor is never quite sure if he’s in some form of hell, “The Impossible Planet” and “The Satan Pit” two-parter remains a weird twist on everything Doctor Who has done before and ever since.
The Ood have a somewhat aggressive role in this story, and it was effective enough that I regretted they weren’t used for villanous means more often.
One can count on one hand the times that modern Doctor Who has scripted a story involving religion, and on one finger the amount of times Satan (or specifically a creature that might be Satan) has appeared.
Perhaps it’s that legacy that has made it a classic, or its use of the criminally underrated Ood species.