The Xeno is the first chest keeper in the Recon Site.
It appears closely resemble to Xenomorph from Alien franchise! It shares skull shape and second mouth out of his tongue. Be careful, it blood is corrosive! Next chest keeper is The Hunter.
After defeating the boss, you receive a 
Blue Chest as a reward. The Xeno may be defeated only once per timeline.
Achievements[]
After defeating The Xeno for the first time, you receive an achievement "Clear Area XVII" which multiplies non-tap monsters' DPS by 1.02.