Corruption cards are a core feature of Back 4 Blood. These cards, randomly drawn at the beginning of a level, change various aspects of the game to make it harder for players. They are an extension to the mission director system found commonly in co-op horde shooters.
There are 10 corruption cards in Back 4 Blood, each adding a unique effect to the upcoming level and the following ones. The corruption cards can be classified into three categories: cards adding more enemies, ones summoning a new kind of Ridden, and ones changing the weather.
Corruption cards adding more enemies
Five Back 4 Blood corruption cards add more enemies to the level: Jogger Swarm, Ridden, Runners, Shambling Ridden Swarm, and Sprinters. Each of these cards summons additional common Ridden, who are easy to defeat but can overwhelm Cleaners who get reckless.
Corruption cards summoning powerful enemies
Four corruption cards add mutated enemies to the game: Hockers, Bruisers, Ogre, and Retches.
Hockers look like normal Ridden, except for their four arms. They can leap forward and hit Cleaners with a glue-like projectile, preventing them from moving, firing, or using their equipment. These mutated Ridden have fairly low health, so make sure to track them down and kill them as soon as possible.
Bruisers are tall mutated Ridden with an overgrown arm they use as a weapon. They are dangerous at close range, as they oversized arm can crush anything and anyone, and Cleaners caught in the impact radius of their strikes are temporarily stunned. If you draw this corruption card, make sure to pack long-ranged weapons to deal with Bruisers more efficiently.
The Ogre is a huge Ridden we meet as a level boss during the Evansburgh campaign. This gigantic zombie comes with a massive health pool and supernatural strength. The Ogre can throw projectiles at the Cleaners and break obstacles in its way. Killing an Ogre is not easy, but you can weaken it by firing at the glowing flesh bulbs on its chest, neck, and back.
Retches are bloated mutated Ridden that vomit on Cleaners. They can throw up a stream of caustic acid, damaging anything or anyone it touches. The vomit also leaves small pools of acid where it lands, causing additional damage to Cleaners who walk through it. Retches are pretty easy to kill so you should make sure to track them down before they can do too much damage.
Corruption cards changing the weather
To date, there is a single corruption card in Back 4 Blood which can change the weather: Mist. This corruption card adds fog to the area, making it harder to see Ridden crawling everywhere.
Bonus corruption cards: special challenges
If most corruption cards bring a disadvantage to your team, some offer challenges you can complete to earn extra copper. Copper is the main resource in Back 4 Blood missions, used to purchase weapons, upgrades, and consumables.
No matter which corruption card comes to hinder your game, you should have the tools to overcome it. The corruption cards stack, meaning the effects of each card will not only affect the level you get them on, but also the ones that come next. Luckily, so do Cleaner cards! As you draw your cards after the corruption, make sure to always have something to offset the negative effects of corruption cards.
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