In the Halo universe, the biggest threat is an alien hegemony called the Covenant. Who are they and what do they want?

A festive auroral display may be put on for a lucky few when coronal mass ejections hit Earth on Christmas Eve and Christmas Day.

Despite this introduction, Earth isn't actually the main setting of Halo 2 — that was saved for Halo 3 — but it was the perfect follow-up to Combat Evolved's completely alien locale.

You know L1 and L2 and polar and MEO. L3 and L4 and halo and GEO. But do you recall, the most famous orbit of all?