Back in 2012, I stumbled across a game called TowerClimb [official site]. It had already been in development for a couple of years and, at the time, a beta had been made available to anyone able and willing to cough up five dollars. That payment entitled the purchaser to a copy of the finished game when it was ready for release. Yesterday, TowerClimb arrived on Steam and although I'd forgotten the name, I remembered the game within a minute of playing. Its randomised vertical levels are as unpredictable and varied as I remember.
If you bought the beta and haven't been able to dig out the original email receipt, you might be able to find assistance in this thread.
And you should try to secure access to the game as soon as possible. Despite some irritating technical issues (as far as I can tell there's no fullscreen, and no way to mute music and sound effects), TowerClimb is a splendid roguelite platformer.
I'm not a very accomplished climber, more of a fell-walker than a mountaineer, so I doubt I've seen even half of what the game has to offer. Not only are there various biomes to discover within the towers, there are also random events, including sudden floods of lava and insect infestations. Initially, I struggled to progress unless the procedural gods were kind, providing plenty of double-jump berries and rocky outcrops that just so happened to resemble staircases.
Once I got the hang of inventory management, carrying an deploying crates as improvised stepladders, I found things slightly less punishing. I've seen wonderful and terrible things as I make my way through the floors, but nothing that quite compares with a pack of hounds pouncing at me, falling short, and landing in a puddle of lava.