Saucer

At night on some occasions you might be surpised from a visitor from above. Keep your animals locked up and alert your neighbors to stay indoors as the only goal the flying Saucer has is to abduct any mob it is able to beam up into itself. It is invincible and is best to wait out till it leaves during the daylight......
(There are plans to expand what happens when you are pulled on board but for now assume it is not good, as even now being pulled into the UFO leads to the death of any player or mob that reaches it's entrance....)