Vipers in the wild are all venomous and this agent's abilities are all aimed at poisoning and disabling the opposing team. She is best known for controlling the environment to provide her team the best chance at success.
Snakebite = Viper fires a projectile that explodes into AOE acid damage. Very similar to Phoenix's hot hands ability but snakebite does do self damage and cannot be curved.
This ability should be used primarily as a crowd control or to get enemies to show themselves from behind structures. Can be bounced off walls or top of map for strategic placement.
Poison Cloud = Equips a powerful gas emitter that activates at the cost of fuel. This will damage all enemies inside the cloud as well as obscure the view in that area from outside. Fuel replenishes when not in use. There is a cool down preventing you from toggling the emitter on and off. Emitter can be picked up and redeployed and it is invisible to enemies as long as they don't see you deploying the emitter. Primary and secondary fire allows you to throw the emitter closer or farther. Emitter can be bounced off the wall or ceiling much like the snakebite ability. Damage in this cloud is considered "decay damage" HP and armor goes down while inside but regenerates when you leave cloud. This damage is non fatal.
This is another ability to help you crowd control a choke-point or objective. You can turn emitter on and on from afar. Similar to cloudburst, it will allow you to position yourself and your team better by obscuring line of sight.
Toxic Screen = Equips a different emitter that shots of line of small gas emitters that you can activate to create a toxic gas wall at the cost of fuel. The range in this ability is beyond comprehension in its current state and will probably be nerfed in some fashion at some point. This wall obscures vision and much like poison cloud, it deals decay damage causing HP and armor to go down while on the wall but both of those will regenerate once outside the wall.
By far the most useful vision obscuring ability in the game. The range is almost from one side of the map to the other. Decay damage isn't the best but this ability will mainly be used to obscure vision and to reposition. Can be picked up and redeployed. You can activate toxic screen in conjunction with poison cloud but fuel will deplete at twice the speed.
Ultimate - Viper's pit = Emits a large cloud of poison in targeted area surrounding Viper. No one is able to see inside the cloud from the outside. Enemies that enter this cloud suffer decay damage and have limited vision. Viper, herself, has enhanced vision while inside. Cloud will stay up indefinitely as long as Viper inside. If Viper leaves the cloud, a "smoke integrity" bar starts to go down. When it runs, out the cloud will start to fade.
Another useful crowd control ability to use especially when protecting a target or when you want to make enemies think twice about entering a specific area.
As a control player, Viper is all about controlling the map as well crowd control. Obscuring vision should be her main priority. While the majority of her abilities aren't lethal, they make the enemy uncomfortable and unsure which can create chaos and confusion. Currently, one of the best supports available.