Helltower (Beta) was an unfinished early version of Helltower.
Helltower (Beta) was laid out in a completely different way to the current one. It was a regular Slender map before turning into the survival/raid map.
Helltower (Beta) was removed when problems arose because of the staircases with no railing, rendering it easy to fall off and take damage. Fire was also randomly thrown in some rooms, making it even harder to avoid the attackers.