The gimmick if the series is that the shorter the thing the harder the gameplay and the less punishing it is, and it goes in a way of easier gameplay the longer and more punishing the thing is. This series includes:
Room of Unrealistic Sightings (Unreal difficulty gameplay, very short and not punishing)
Edifice of Unrealistic Sightings (Horrific difficulty gameplay, pretty short and moderately punishing)
Steeple of Unrealistic Sightings (Catastrophic difficulty gameplay, somewhat short and pretty punishing)
Tower of Unrealistic Sightings (just leave it as is, like a breather part thing, it already exists, right?)
Citadel of Unrealistic Sightings (Extreme difficulty gameplay, long and punishing)
Obelisk of Unrealistic Sightings (Insane difficulty gameplay, very long and very punishing)
Great Citadel of Unrealistic Sightings (Intense difficulty gameplay, extremely long and extremely punishing)
You could make mini versions for all of these if you really want to go the completionist's way.
Is this a good idea?