Penumbra is frictional games first,...... game. The first one is about a guy named Phillip walking around an underground mine being scared of everything. (I.e Spiders, haunted dogs and a giant rock worm). you'll even get you own torch that you will never use! The second one is about him being scared in a lab. (I.e weird mutant people, spiders and a giant rock worm) And the last one is just an expansion that wraps everything up. It like amnesia with its physics puzzles and focuses on running from the enemy and throwing beef jerky at dogs. Despite being able to kill things. The second one is scarier because you can't fight back and the monsters talk. They aren't as scary as amnesia but i had fun playing them.
here's a sort of trailer