It's the nether but with a theme of ice. The monsters you've fought in the nether have adapted to the reversal of thermal temperatures and as a result some have mutated or otherwise evolved to survive.

This is primarily a texture pack you'll enable just to get a kick out of then disable once you've seen everything, however I have designed it so it should all tie in together so it can function as a permanent experience.

Optifine required to see fog & appropriately renamed items.
Faithful (32x) highly recommended to be equipped underneath this pack, though not required.