Poltergeist Mob (Disrupter)

This could be a mob much like the silverfish that could inhabit any block in the world. They could have a low spawn rate, but are generated when the world is generated. However, unlike the silverfish, you cannot hit them out of the blocks. During full moons, all the poltergeists in the world leave their blocks and disrupt the world in some way. They could break wheat a player has been growing, make a creeper charged, make passive mobs hostile, ect. They can be killed while they are causing mayhem during the full moon, but they go back into random blocks when the sun comes up. Depending on the effects the poltergeists have on the world, they could be anywhere from a minor annoyance to a major problem. If they are very annoying (having large effects), there should be a way to find out what blocks they inhabit to move the block they reside in somewhere else. Since the phases of the moon are already implemented but does not have a large effect on the game, adding a mob like the poltergeist could make players have to think about being out and about without preparing in advanced, especially since mobs are generally more dangerous during the full moon.