His ability to repair at any time, paired with his turret ability make Bastion a crucial member of any defensive strategy.
Configuration Recon: Bastion plays like a slower Soldier: 76 in this mode, free to roam around the map and armed with a submachinegun with a medium damage output and range.
Configuration Sentry: In this stationary configuration, Bastion deals heavy damage with great range, allowing him to dismantle entire groups of enemies with ease.
Reconfigure: This ability is used to swap between the two modes.
Self-Repair: Bastion can repair his body with this ability, though he cannot move or fire his weapon while this is active.
Configuration Tank: Bastion extends a set of treads under him which allow him to maneuver around the map quickly while dealing massive damage with his long range explosive shells.
You should almost always be in Sentry mode as Bastion, as his alternate mode is comparable to a lower DPS version of 76. With Bastion, you're going to be looking for a choke point, a position in which the enemy must (or at least is very likely to) travel through. For escort missions, securing a location 50 yards in front of the target is your best bet, as the enemy will be funneled through the area, unaware of your placement. It's also recommended that you don't stay in one place for too long. Generally, you're going to want to change positions every time you have the opportunity to. This will keep the opposing team guessing, which is paramount, as an immobile Bastion is a sitting duck for long range attacks. As for the ultimate ability, the tank mode, it's best to use this in close proximity though it has great range for long distance shots. Rolling into a tight space as the tank and surprising a couple members of the opposing team can turn the tide of battle, as each shot does both impact and splash damage, making it easy to eliminate entire groups of foes.
After dealing with an enemy in Sentry mode, move on to another location in Recon mode. This will keep the opposing team from narrowing in on your position.
McCree: With McCree’s short range for high damage and inability to traverse the environment easily, he’s an easy target for Bastions Sentry form.
Mercy: Her low health makes her an easy target, and can regardless of her flight path is an easy target for Bastions turret.
Winston: Although Winston has a decent amount of health, his weapons are close range and because of this, Bastions high rate of fire and heavy damage output can easily make Winston fall in battle.
Tracer: Though bastion can easily tear through Tracers health, if she can close in on you, she can make quick work of your health meter regardless of your formation.
Widomaker: Widowmaker can easily take down Bastion with a single well-placed shot to Bastions weak point on the back of the sentry mode.
Mei: Her ice wall ability can serve as not only a protective barrier between Bastion and the opposing team, but also as a way to easily sneak up on Bastion, freezing him and finishing him off.
Real Name: SST Laboratories Siege Automaton E54, “Bastion”
Occupation: Battle Automaton
Base of Operations: Unknown
Once a frontline combatant in the devastating Omnic Crisis, this curious Bastion unit now explores the world, fascinated by nature but wary of a fearful humanity.
Originally created for peacekeeping purposes, Bastion robot units possessed the unique ability to rapidly reconfigure themselves into an assault-cannon mode. But during the Omnic Crisis, they were turned against their human makers, forming the bulk of the omnics' rebel army. Following the resolution of the crisis, nearly all of them were destroyed or disassembled. To this day, Bastion units still symbolize the horrors of the conflict.
One unique Bastion unit, severely damaged in the final battles of the war, was left forgotten for over a decade. It lay dormant, exposed to the elements and rusting while nature slowly reclaimed it. Overgrown with vines and roots and nested upon by small animals, the robot sat inert, seemingly unaware of the passing of time. That was until one fateful day, when it unexpectedly reactivated. With its combat programming all but lost, it instead displayed an intense curiosity about the natural world and its inhabitants. This inquisitive Bastion unit set out to explore its surroundings and discover its purpose on a war-ravaged planet.
Though "Bastion" appears to be gentle—even harmless, at times—its core combat programming takes over when the unit senses danger, utilizing its entire arsenal to eliminate anything it perceives as a threat. This has led to instances of conflict with the few humans it has encountered, and has driven it to avoid populated areas in favor of the wild, uncharted regions of the world.