Twilight Forest

The Twilight Forest is a mod created by Benimatic that adds a new heavily forested dimension called the Twilight forest to your Minecraft/Feed the Beast world. As the name implies, the Twilight Forest is densely forested and in a perpetual twilight; the normal day-night cycle is suspended. An overstory of larger trees further shades most of the world below. The canopy is pierced only occasionally by massive trees that rise to the ceiling of the world. The terrain is flatter, or at least less mountainous than Vanilla Minecraft, but featuring occasional hills, sometimes rising far above the canopy level. These hills are hollow, containing caves filled with valuable ores, treasure, and dangerous monsters.

In addition to the new dimension, this mod also adds dungeons and bosses, as well as a number of new items, trees, and numerous mobs.

Entering the Twilight
Entering the Twilight Forest is achieved through the creation of a Twilight Forest Portal. A 2x2 pool of water only 1 block deep forms the basis for this portal; additionally it must be surrounded by "natural" vegetation including flowers, grass, saplings, and mushrooms. Once the pool is surrounded in this manner, the portal is completed by dropping a diamond (pressing Q by default) into the water. The water will turn purple (similar to a Nether Portal) and a bolt of lightning will strike the portal, inflicting minor damage to nearby players. Players may travel to the Twilight Forest by walking or jumping into the newly created portal. Once the portal is activated, it is possible to remove the flowers around it while keeping the portal intact.

Progression
The majority of the Twilight Forest is a peaceful biome. Despite the perpetually dim conditions, hostile mobs will not spawn on the surface in the Twilight Forest itself. Instead, progression through the mod is centered around landmarks that serve to advance the level of difficulty encountered through increasingly challenging enemies and bosses. Chest items and drops become correspondingly more rewarding with each new area. It should be noted that Twilight Forest Portals will not discriminate as to the area in which they appear; a newly created portal may bring the player to the interior of a Hollow Hill or even one of the various Twilight Forest boss lairs. As such, some degree of caution and preparation should be exercised when first passing through a Twilight Forest Portal.

Guides

 * Getting Started with Twilight Forest