Dark Tower
These colossal towers can only be found acceding out of a Dark Forest. There are many unique floors, themes, obstacles, treasure, and monsters which you can find throughout the Dark Tower. The entrance of the Dark Tower is made up of Reappearing Blocks, and can be found by traveling through the Dark Forest.
Dark Towers resemble Lich Towers, but are instead much larger, and made up of many different types of Towerwood, an almost unbreakable wood found in, mossy, infested, cracked, and encased. Adventures may also find many strange and unique items and blocks such as,Netherrack, Soul Sand, Nether Wart, Redstone Lamps, and more. Some of the towers connected to the Dark Tower are is also made out of Netherbursts.
Below you can see an example of a Netherburst.
There are many different rooms, floors, and towers that make up the Dark Towers. These rooms may contain monster spawners, but also many unique treasures such as, Enchanted Books, Steeleaf, Ironwood, Redstone, Diamonds, and more. One special treasure that you can find in these chests are Tower Keys. In order to travel to the top of the Dark Tower, one must search the many floors and towers, looking for the four Tower Keys to complete the Locked Vanishing Block doors.
The mobs that inhabit the Dark Towers are Skeletons, Creepers, Endermen, Blazes, Pinch Beetles, Carminite Ghastguards (spawning outside the tower), Carminite Ghastlings, Carminite Golems, Towerwood Borers, and Carminite Broodlings. The Carminite Monsters and the Towerwood Borer can only be found in the Dark Tower.
Finally, the peak of the Dark Tower in covered in Netherbursts and is home to the terrifying Ur-ghast. The Ur-ghast is a gigantic creature with long tentacles with blood on them. The Ur-ghast will fire fireballs, summon minions, and stay at the peak of the Dark Tower until defended. Upon the Ur-ghast's defeat, a treasure chest will spawn in the middle of the peak containing valuable treasure.
Below you can see pictures from the middle and bottom of the Dark Tower.
Progression
Using the progression system, you will need to have defeated the Hydra before entering the Dark Forest. Additionally, the dark tower, and all of its blocks and monsters will be protected until the player has defeated the Knight Phantoms.
Destroying the Ur-ghast and obtaining some of its Fiery Tears will magically dispel the blizzard surrounding the Snowy Forest.