Junkertown is being invaded by an endless army! Keep them from killing the hero they've come for! If the hero or all of the players die you lose. As you defend the hero you'll progress to higher rounds and unlock new enemies. This mode currently supports all 32 heroes with unique attacking styles as enemies. Once you've unlocked all of the enemies you'll have to escort the hero to the safe zone in a unique round format. If you succeed you'll have to defend a new hero and the enemies will begin to spawn with modifiers. The players get to choose a modifier as well! Modifiers change the behavior and stats of a hero. The modifiers are:
Durable - Gain more health at the cost of doing less damage and healing
Deadly - Gain more damage and healing at the cost of having less health
Life Stealing - Doing damage or healing heals you
Fast - Gain a higher movement speed at the cost of slightly lowered health, damage, and healing
Strong - Move slower in exchange for increased damage, healing and health
Exploding - When you die you explode, doing damage to enemies around you
Floating - Jump higher and stay in the air longer, enemies with this modifier jump frequently
Burning - Apply damage over time or healing over time to everything you interact with at the cost of slightly lowered health, damage, and healing
Once all the modifiers are unlocked enemies will start to behave differently. These alternate form enemies attack differently, but have similar strength to regular enemies. After they're all unlocked each player's modifier is upgraded. Each modifier has a unique upgrade:
Upgraded Durable - Pressing Interact while looking at a teammate will form a Health Link. While a Health Link is active all of the damage dealt to the target of your Health Link will instead be dealt to you.
Upgraded Deadly - Cooldowns are twice as fast, but your health is further reduced
Upgraded Life Stealing - Heal nearby teammates in addition to yourself by doing damage or healing
Upgraded Fast - Jumping while moving forward does a quick angled jump that allows you to move faster
Upgraded Strong - Doing damage knocks back enemies
Upgraded Exploding - The death explosion also heals allies to give the team a better chance of getting a successful revive
Upgraded Floating - Gain additional jumps and the ability to carry a teammate into the air with you
Upgraded Burning - While the burning effect is active it can be spread further by the affected player doing damage or healing. The effect damages enemies and heals allies. Only players that got the burning effect from the player with the burning modifier can spread it.
Modifier upgrades also come with Ultimate Form enemies. Ultimate Form enemies are similar to Alternate Form enemies except the changes in Ultimate Form enemies make them stronger. Beating them will require a good combination of hero and upgraded modifier.
This mode doesn't just spawn a bunch of enemy heroes purely at random. There's 4 subtypes of enemies that make up each wave.
Regular Troops - Regular troops are the most commonly spawned enemy and aren't particularly threatening alone. A few examples are basic Soldier 76s that just shoot and Ashes that just throw dynamite after a while.
Tanks - Tanks are the second most common and unlocked shortly after starting. The Tank enemy class isn't the same as the Tank class in the actual game. Reaper and Brigitte are members of the Tank class in this gamemode. They typically spawn with a group of regular troops and have more health and damage than the regular troops.
Minibosses - Minibosses are the second rarest enemy type. They aren't unlocked until a few rounds are completed and spawn rarely if at all. They're essentially members of the Tank enemy class with special utility. Lucio for example speed boosts other enemies and Zenyatta applies his Discord Orb to players.
Bosses - Bosses are the rarest enemy type. They're locked until several rounds have been completed and typically will only spawn once during a round if a boss is going to spawn during that round. The Boss enemy class is made entirely of heroes from the Tank class in the regular game. Some bosses are just big enemies with lots of health and damage like Roadhog. Other bosses have unique abilities like Orisa's ability to stomp the ground and launch players into the air.
Overall this is meant to make each round feel unique.
This mode also includes difficulty settings. The difficulty of the mode can be set in the spawn room by the host player before the game starts using the primary and secondary fire buttons. Higher numbers mean more difficulty. This affects the strength of the enemies as well as the hero that's picked for you to defend. Every hero is available for players to pick unmodified at the start of the game. Excluding Torbjorn and Symmetra's turrets, which can't be targeted by the enemies and were disabled as a result. The hero you're defending responds to some communications like group up. If no settings are selected by the host player in the spawn room the game will start at normal difficulty. Teammates can be revived by standing in the yellow circle where they died. By default this mode ends at round 30, but counts as a victory once the first hero you're defending is successfully escorted to the safe zone.