Viper

Viper the Netherdrake is a ranged agility Hero who can function as an excellent ganker and carry due to his slowing auto-attacks and his low cooldown ultimate. Although ganking is often made easier with Viper's presence, his true carry potential is revealed with sheer item power. Farming with Viper is relatively easy; while he has no area of effect abilities to clear waves, Nethertoxin makes last-hitting a cinch. However, active participation in ganking is very important before his ganking power wears out in mid-late game, due to enemy heroes playing more cautiously and obtaining better items. Poison Attack makes Viper very potent in hero harassing.

Tips

 * Poison Attack max is the best way to slow and damage a target of your choice and doesn't require your opponents to attack you for the skill to be applied. If you're in a lane with supports, this is probably the strongest choice.
 * Nethertoxin is the generally weakest option to max, but if the rest of your team is capable of getting your opponents to low HP quickly, this will allow you to easily clean up fights. It's a good choice to pick up early if you want to last-hit easier.
 * Corrosive Skin is the best choice to max first if you'll be in situations where you and your opponent(s) will be trading blows, rather than you just attacking. The damage per level of this skill is roughly the same as Poison Attack, but greatly increases how tanky you are.
 * Corrosive Skin is especially potent against DoT spells. Between the magic resistance and continuous reapplication of Corrosive Skin to the caster of the DoT, Viper will usually take less damage than Corrosive Skin returns.
 * As your Poison Attack and Viper Strike slow attack speed as well, apply them to the enemy carry to cripple their damage output.
 * Late-game, Viper can help push by tanking the enemy creep wave, thanks to the damage return of Corrosive Skin. Of course, the enemy heroes' position should be taken into account.
 * Viper is great at kiting melee carries with his large variety of slows and with an Aghanim's Scepter.

Trivia

 * Viper's response "Holy shit, it's me!" is a reference to the movie Top Gun. Gyrocopter makes a similar, yet more accurate response upon meeting him as an ally.