Alien Hunters DLC (XCOM2)
Alien Hunters is a DLC for XCOM 2. It adds a storyline mission, after which the Commander will encounter elite alien rulers randomly in missions. Defeating the alien rulers grants special weapons and items.
The Avenger receives a garbled radio transmission that appears to bear the signature of the original Skyranger. Cleaning up the transmission reveals a voice that may be Dr. Vahlen's. Bradford authorises a mission to rescue Vahlen. Despite misgivings about her... extreme... research practices, her genius could be a huge asset to the resistance.
Bradford personally accompanies the squad on this mission. He is a Ranger with high HP and access to several advanced techniques. The squad approaches the research site and quickly encounters juvenile Vipers with low HP and only melee attacks. Bradford's Reaper ability is extremely effective against these creatures, as they are weak but numerous.
As the squad proceeds through the facility they hear recordings from Vahlen about her research in to the original, unmodified genetic structure of the alien races. They also encounter displays detailing her creation of three "Ruler" aliens, and recordings describing alarmingly intelligent behaviour on their part.
Reaching the final chamber, the squad find a containment chamber that has been breached, with a body in the middle of it. They also hear the ungarbled transmission being broadcast - a warning that the test subjects have escaped and to stay away. Bradford decides that having come this far, he must know if the body in the containment cell is Vahlen's. Upon approaching the cell, the Viper King ambushes the squad. After taking some damage the Viper King teleports away and the squad fully investigate the cell, finding that the body is not Vahlen's, and no trace of her.
Alien Rulers have the unique Ruler Reaction ability, where they will take a reaction for every action your soldiers take on your turn. This greatly complicates many strategies that would work against other aliens - for example, flanking them is very difficult, because they can move or attack the flanking soldier between moving in to position and firing.
Between this, and the ruler's ability to turn up randomly in missions to complicate them, means this DLC can greatly increase the difficulty of the campaign.
When an alien ruler takes enough damage they will summon a psi-gate and try to escape. If they make it they will return in a later mission with less than maximum HP, proportional to how much they had when they escaped. In this way they can be whittled down and killed over several encounters.
The DLC allows the creation of 4 unique weapons designed to combat the alien rulers. Upon defeating the rulers, autopsying them gives access to unique, powerful armour sets.