Ender Invasion

The Ender Invasion is a conflict between the endermen of the End and the Overworld.

Past
The Ender Invasion began before the age of humans, when the ender dragon started sending his endermen to the Overworld. They used their teleportational abilities to reach the Skylands and conquer it. Then they proceeded to the Overworld and began inspecting its materials and inhabitants. The then-people of the Overworld began slaying the invasive endermen and examining their bodies and magic. From the ender pearls and materials brought to the Overworld by the endermen, they constructed portals, but they were eliminated before using them and their strongholds abandoned. However, a small group of invaders may have entered the End and built the End cities.

Present
The humans eventually made their way to the strongholds and activated the portals, allowing them to reach the End by themselves. They were able to destroy the dragon's protection and finally kill him, creating another portal in the End well to lead them back. Only thing left behind by the dragon was his egg.

Possible future
In response to their master being killed, the endermen are bringing endermites, small ender pests, to the Overworld. This action could lead to a full ender plague on the Overworld.