The Combine (KOM-bine) is a cruel, inter-dimensional empire composed of many species-- some allied, and some enslaved. It seeks to expand its dominion and assimilate species into itself (hence the name). The Xen lifeforms came to Earth not to invade, but to escape from the Combine. Unfortunately, however, the Combine followed them, invading and overwhelming Earth in just seven hours. The Combine went on to lay waste to Earth and to the human race, and it assimilated many humans into its on-world military, the Combine Overwatch. The Combine is the main antagonist force in Half-Life: Alyx, as well as in Half-Life 2 and its episodes.