Viper is one of my favorite carries, and because he is mainly a right-click hero, he is easy to learn. His abilities slow enemies and apply damage over time. The longer a team fight lasts, the more like he'll come out on top. Enemies need to burst Viper down quickly, but doing so risks letting the rest of your team counter. Once you farm a Heart, you'll be one of the tankiest agility heroes in the game, with only Naga Siren, Spectre, and Medusa being more durable.