Featuring 3 new Alien Rulers, the Alien Hunters DLC is available across all regions and platforms. Previously, Firaxis Games and 2K have released a lot of information about the DLC. All 3 bosses were described by the developers in their developer blogs. Check the following articles to know more about the released content: the Archon King reveal, (with the description of his abilities) and the Berserker Queen reveal (with the description of her abilities). You might also want to check the info on Viper King.
The Alien Hunters DLC also has its own trailer, so, here it is: