Showdown Strategy Guide

Intro
Showdown is the last mission in Chapter 1. It is the first boss-style encounter in the game, and as such is considerably more difficult than all the prior runs. The fight has three distinct phases (though the last phase can be skipped) and culminates with a choice to either kill or save Jane. The fight begins once the main room is entered--you can buff and the like for as many turns as you want.

Cover, Line of Sight, and the Cone Attack
In every phase of the fight, the boss (who attacks last) fires off waves of green. Each wave affects one of the six wedges of the room. If one of these waves hits, it does 11-13 physical damage. It is a base 100% to hit attack, which is reduced by cover. Since it can't even target things the boss does not have line of sight to, it is recommended to keep out of the boss's line of sight at all times unless actually attacking the boss. If nobody in the party is in the boss's line of sight, then the boss won't even be drawn; this can be a way to tell if everyone is safe.

Phase 1
When the fight begins in phase most of the party is still in a small room adjacent to the boss's room. The boss is in the center of the main room, surrounded by a green force field. The center of the room and the two cover spots at the entrance are exposed to the boss, the rest is safe and can be a good place for the party to weather transitions. The boss attacks with one wave this phase.

There are three generators spread out around the room. Destroying these generators is what lowers the force field and begins phase 2.

The boss will summon one wave of dogs on turn two. The boss will also summon a wave of dogs for each generator destroyed in the previous round. (So long as it's still phase 1.) Thus you do not get dogs for entering phase 2, and if you kill all three generators on the same turn as you first entered the main room you can avoid the dogs completely. These dogs have 8 hp and attack for 3, however they are one of the most dangerous parts of this fight because they can also do an AOE fear which can move people into the boss's cone attack.

Thus a way to handle phase 1 is:
 * Take positions out of the boss's line of sight and wait for the first round of dogs.
 * After defeating them, kill the generator opposite the entry room.
 * Deal with the dogs the boss summons in response
 * Have everyone return to the entry area
 * Destroy the second generator
 * Deal with the dogs
 * At this point, the party can rest and get all their cooldowns back before beginning phase 2
 * Once ready, destroy the third generator, making sure everyone is in a safe place for phase 2

Phase 2
Once the third generator is destroyed, the boss's force field bubble vanishes, damaging the boss for 5 hp (leaving her at 315/320.) In response, the boss removes 4/6 of the cover from the room, brings in 8 incredibly long-range turrets, and now attacks with two waves of green each turn. Phase 2 lasts until the boss is below half, though if you can defeat the boss in phase 2, you will avoid phase 3. This is advisable. The room is divided into six wedges, as demarcated by green lines on the floor. The wedge nearest the entry room and the one counter-clockwise of it are the cover that are available at the beginning of phase 2. Thus you want everyone either in the entry room or near that cover at the start of phase 2. Furthermore, those turrets are pretty lethal, so you don't want anyone exposed to more than one when it's the turrets' turn.

The available cover then changes each round of combat. It effectively moves one wedge clockwise each round. There will also be green walls around the boss in various patterns. These walls can also be used to avoid the boss's cone attack and hide from turrets. The cover moves after the green cone attack, so you can hide behind the cover that is about to disappear.

A way to handle phase 2 is:
 * Phase 2 is triggered as the first action in a turn, leaving everyone with move and attacks.
 * A turret team is chosen, which are people that have decent move and firepower to destroy turrets. Everyone else waits in the entry room. Rigged Intruder drones are excellent at this.
 * The turret team moves with cover clockwise around the room, destroying each pair of turrets they come to. Ideally, the turrets never have a shot at anyone
 * Once all the turrets are dead, the boss is carefully attacked down to about 180 health. Do not pass half health!
 * Make sure everyone has reloaded and all burst damage cooldowns are available
 * Burst the boss down to 0 in one turn.

Phase 3
If the party ends their turn with the boss alive but below half health, phase 3 begins. Phase 3 begins by the boss hitting the room with a cyan stun attack (actually two 180 degree attacks.) It can miss people with cover, but it advisable to be out of sight. The boss also summons a pack of minions with a Hive Controller, Suicide Bomber, etc. Lastly, the green walls that had been next to the boss disappear, reducing the available safe zones in the arena.

The Choice
Once Jane is defeated, she lies gasping on her platform and a Destruction icon appears for anyone with actions left. In addition, the exit rectangle appears. Anyone in the party (no skill needed) can use that Destruction icon to kill Jane and end the mission. Alternately, the surviving party members can enter the exit rectangle to end the mission and save Jane.

Especially when pugging, it's easy for someone to try to loot Jane and thus kill Jane even if the party leader wanted to save Jane. Saving Jane takes the cooperation of the entire party.

The ended text says that each party which completes the run is casting a vote for the canonical ending of the mission. Given how easy it is to kill Jane, that is likely to be the winner.