Frostenhorn is Shiverthorn server area to achieve hard achievements such as 1 km rail, help each other get "When pigs can fly" and other lesser achievements if you haven't got them yet. Also Frostenhorn has it's own wolf-house, slime spawn and fishing spot which doesn't freeze to ice! Frostenhorn is an exceptional area to farm, in the basement there's sugar cane-, mushroom-, cactus- and grain-farms.
There's one entrance behind the mushroom farm which will direct you to a gigantic mine, which you can dig out, look for monsters and try to see if there's any minerals worth mining for your own use. To get to Frostenhorn, you have to take the small portal which leads to the "Temple of Crossing Roads", and then take another portal to Frostenhorn. The "Temple of Crossing Roads only has 2 portals, one leading back to spawn poin, and the other one leading to Frostenhorn. When arriving after using the portal, you will see that you're in a room, the room is the to protect you from creepers, skeletons and other pests in Minecraft.
After opening the door leading outside, you will see the wolf-house to the left, stairs leading up to fishing pond, and then, in front of you, you will see the "base" of Frostenhorn. Inside the base, there is a few bedrooms, some chests, a crafting table and a few furnaces on the ground floor, there is also a lava-trash-can made for you to get rid of uneccesary materials, and a ladder up and down.
If you take the ladder upstairs, you will first get to the watch-tower, then right above is "The Rail" (A 1 km rail) for transportation to the greenlands. And in the basement is the farms. To get to the "secret" slime-room, you have to press a button at the cactus-collection-area, and two pistons will open a door for you, but be fast, you barely got time to get through! The slime room is 4 chunks big, (1024 blocks of flooring) this is then a massive slime spawn, for your own amusement and challenge.