The demonic planes of hell are many, although the exact amount is unknown to any, as even the highest Demon Masters keep the amount of planes under their control hidden from others. A subspace plane can be the size of a small room, or large enough to fit a sprawling city inside. Each one has to connect to another plane or to our world, or else they are lost forever.
It is said there was once uncountable planes, made before The Fall, but without the creator they are inaccessible.
Very recently one small plane holding pre-Fall weaponry was found, and we are delighted to begin incorporating it into our operations. However as tempting as it may be to use such items liberally, it must be noted that these artifacts are irreplaceable, and immensely holy.
If it came to a point where you would lose either a number of humans, or one of these tools of the creator...
Hard times. Hard decisions.
-Notes from the Meeting of Angels