Who the frack is the Aten?

The "boy king" how he is often called lived in turbulent times after his supposed father Akhenaten banned the Egyptian Pantheon of Gods and prayed to only one God, the one - and only - the Aten. The Aten was no new god. 

He was worshipped as the sun disc - an aspect of the sun god Ra - before he was promoted to the supreme deity. We don't know for sure, if Atenism was the first real monotheistic religion or if the other gods still played a (very) minor role in some form, something religious scholars call "henotheism". The real goal of Akhenaten and his Great Royal Wife Nefertiti was supposedly to remove the all-powerful priesthoods, notably the one of Amun in Thebes, by establishing themselves as sole intermediary between the Aten and the people.

He even quit Thebes and built a completely new city in the dessert some 300 km North at Tell-el-Amarna. This is also why this time period is called "Amarna Period". The Pharao called the new city Akhetaten, meaning the "horizon of the Aten". The whole administration and the nobles where moved to the new city and within