In general:
This mod adds the new Endplains biome to your world. It is a small biome which can have structures, and many endermans at night. It adds some tools, Eyes of enderman which you can crush into the new item: the Enderidian. You can craft those into the tools. Enderman have a chance to drop their souls and eyes. If you combine them, you get the opened eye of enderman. This is the eye you can crush into enderidian.
Biome:
The biome isn´t pretty rare to find. At night there are many endermen, so you got to be carefull not to look in their eyes. It has 3 different structures. The ruin, the house and the blacksmith. These are not part of one big village, because the loot would be too much. Every structure contains one secret chest, so you gotta watch out.
Items:
eyes/souls of enderman can be dropped from endermen. Combine them together and you get the Opened eye of enderman. With 2 opened eyes, 2 souls and 5 obsidian you can craft the CRUSHER. This item is important for the tools. If you put opened eyes in there and press "CRUSH" you will get the enderidian to craft the tools with.
Blocks:
There is a completely new wood type called "enderwood". You can use it just as normal wood and craft wooden tools, sticks etc. Also you can craft it into stairs, slabs, fences etc. just like every other wood.