Little is known about the Neanderthal Multiverse Empire (NME) from the backstory of AH.com The Series. Two facts remain certain :
1.) The NME was founded by a civilisation of space and multiverse exploring Neanderthals. The civilisation originated in a timeline where Neanderthals became the dominant human species in Earth's prehistory and achieved considerable technological and cultural advancements since then. Its last emperor was Ponter, who was followed by the brief rule-in-exile of his daughter Atta.
2.) The NME was the original creator of much of the technology behind the MES class of shift-capable, multiverse-faring starships. When the human multiverse polity known as Human Unity won a minor multiverse war against the NME, it was left with several MES class ships in its possession, all of them requisitioned from captured NME armed forces stocks. The most famous trio of these ships were the AlternateHistory.com, the CounterFactual.net and the AlterVerse.net. A related, more advanced, apparently prototype ship of the Neanderthal Fleet was the Ponter, named in honour of the emperor.
The names of some of the Neanderthal characters (e.g. Ponter), and the idea of Neanderthals becoming the dominant human species in an ATL is a homage to Robert J. Sawyer's The Neanderthal Parallax trilogy of novels. This homage is rather deliberately ironic, since most AH.commers disliked a lot of Sawyer's plotting and characterisation in that novel series.