Cursed Gym (of Doooom) (Patreon)

This was to be paired with a story that I unfortunately never finished.  The general idea was a couple of gals head into a gym to try it out.  Place is immense once they go inside.
Unnaturally so.  It's cursed as all get out (naturally), and after a couple hours of trying out some exercises they notice the exit just... Isn't there anymore.  Every now and then, they swear they can see other people just out of the corner of their eye, but when they turn, there's no one there.  Even weirder, they looked awfully big for humans...

Longer they stay in the place, the more they change into buff muscle tigers, and can't remember their old selves.  The gym becomes their life kinda thing, with them moving ever deeper into the dense jungle of gym machines.  Woulda ended with the next group unsuspecting girls coming in and, as you'd expect, catching a glimpse of a couple figures in the corner of their eyes.  Probably nothing to worry about.