XCOM 2
87 Achievements
Viper Vanquisher
Kill the Viper Ruler
11.8%
How to unlock the Viper Vanquisher achievement in XCOM 2 - Definitive Guide
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It will be the first alien ruler you encounter if you´ve enabled the mission "Alien Nest" at the beginning of your playthrough. If you have not enabled the mission, which alien ruler you encounter first will be random.
Like all other alien rulers, the Viper King performs one action after every action made by XCOM during a special Ruler Reaction phase. Some abilities do not trigger Ruler Reaction, like Lightning Hands or Bladestorm.
At some point, when enough damage has been dealt to it, it will open a portal and attempt to escape (if you kill it as it attempts to escape, you will get the achievement "Not throwing away my shot" if you don´t have it already). If it escapes succesfully you will randomly encounter it in a future mission, but it's health will be the same as last time, it does not regenerate.
It is unlikely you´ll be able to defeat it during your first encounter, however, if you manage to do it, you will get the achievement "Regicide" if you don´t already have it.
Here is the strategy for fighting the Viper King:
He has four attacks:
1. Bind and Crush: grabs a squadmate, deals damage and has a 50% chance to render unconscious.
2. Tongue Pull: same as Bind and Crushed, but ranged.
3. Frostbite: AoE ranged attack that freezes units for two turns.
4. Bolt Caster: shoots you with his bolt caster.
General tips:
-Take off its armor ASAP.
-Hit him with effects that do damage over time, like burning or poison. It will take damage in every reaction phase.
-You can counter Ruler Reaction with flashbangs, frost bombs or attacks which can stun.
-Try to fight it when it's alone. If possible kill all other nearby enemies first.
-Do not group your squad too close together, to prevent multiple of them getting frozen.
-Move as little as possible. Try to use all your actions to attack.
-Use free actions as much as you can.
-You can use the
button to end your turn manually and get back actions from soldiers who already used their actions.-Psi Op's Stasis ability will lock the Viper King down for an entire turn.
-If War of the Chosen is installed, the ability Dual Strike, available when two soldiers have a level 3 bond, can be extremely useful.
Cassylvania, JAKKRIEG
The Viper King is the first of the three alien rulers. He is weaker than the other alien rulers but far more powerful than an ordinary Viper. He has a ton of health (44 on Rookie and 69 on Legend) and some very strong abilities. Like other Vipers, he can use Tongue Pull to bind a soldier but his version has a 50% chance to knock that soldier unconscious with every tick. What’s a "tick"? Well, you know how enemy soldiers always wait until you are finished taking your turn before taking theirs? Yeah, the alien rulers don’t play by those rules. They have a special ability called "Ruler Reaction" that allows them to react after every action you take. If you take a shot, move a soldier, even reload your gun, the alien ruler will get to take an action as well. That means a soldier that is bound has a 50% to be knocked unconscious after every action you take. The Viper King also has an area-of-effect attack that can freeze any units caught in the blast for two turns.
To kill the Viper King, you want to focus on doing as much damage as possible with every shot. Limit the amount of Ruler Reactions he can take. If he suffers enough damage, then he will open a portal and escape from battle. It's not over there, though. There is a chance on any future mission that the Viper King will be present. Any damage you have done to him will carry over but you will have to kill him to keep him from reappearing again and to get this trophy!