Serious Sam Revolution - Alpine Mists 2: Dusts of Ages pt.2 (Serious) 

Alpine Mists is a three-levels campaign set in different environments. This is the third and last level, it keeps the good variety of environments like the one before and a good level of challenge, although this one was not that difficult even at Serious. Thanks to the creator RatBoy and to Emperor Longcat for republishing it
Steam's workshop page:
steamcommunity...
I've played this map in blind run at Serious difficulty. When you see the fades, it generally means that I've died there, or that I went back somewhere to pick up some stuff or that I've reloaded 'cause I let myself be hit too much in stupid ways