Boss Sibelons are the hardest alien found in the Lower Maps and have the most health and damage of the Lowers Aliens.
Boss Sibelon are the harder version of the original Sibelon and are found in the Lower Maps. They normally require a lot of patience to kill, as they have a lot of health and are difficult to bring down in a non Full-Eliteship. It is recommended that you get a number of outfit members to assist you, as you can easily be killed while fighting one - either by the Alien, an enemy player, or a notorious Company Killer. After you finish killing it, you and your outfit members (if you are going solo you get it all) will get a good reward along with the large cargo drop.