Dota 2/Lesale Deathbringer the Venomancer

Venomancer is a ranged agility hero who is usually played as a support and pusher. He can deal a lot of damage over time with his abilities. His Venomous Gale and Poison Sting gives him good slows which can hinder an enemy's escape. His Plague Wards are very useful, letting him push, defend and gives vision. Finally, he can use his ultimate, Poison Nova, to quickly burn away his enemy's health.

Venomous Gale
Venomous Gale makes you shoot a ball of venom at the direction of the targeted area, allowing enemies and doing damage to enemies in its path. It also poisons affected enemies after level 2, making them take additional damage over time. A 50% slow is pretty powerful, and is usually enough to make sure an enemy doesn't survive a gank. If they do manage to escape, they will still have had taken damage from the venom.
 * Ability: Target Point
 * Damage Type: Magical
 * Duration: 15
 * Strike Damage: 25 / 50 / 75 / 100
 * Damage Over Time: 0 / 30 / 60 / 90
 * Slow: 50%
 * Mana Cost: 125
 * Cooldown: 22

Poison Sting
Poison Sting makes your normal attacks poison enemies, slowing them and doing damage over time. A 14% slow is very good for a passive ability, especially since an Orb of Venom will only give you a 4% slow for ranged heroes. It lets you effectively chase down enemies and finish them off with the venom.
 * Ability: Passive
 * Damage Type: Magical
 * Duration: 6 / 8 / 10 / 12
 * Damage Over Time: 5 / 10 / 15 / 20
 * Slow: 11% / 12% / 13% / 14%

Plague Ward
Creates a plague ward at the targeted area that attacks enemy units and structures. It does piercing damage, so it will do increased damage to lane creeps and reduced damage against anything else. The wards will also inflict 50% of the current level of Poison Sting damage on enemies it attacks, but this can be overridden by Venomancer's own Poison Sting. This is your most useful ability, and what Venomancer is known for. With a mere 5 second cooldown and costing a negligible 20 mana, you can place a bunch of them to take down creep waves, which is useful during pushes or when defending towers. With a ridiculous hp of 450 at level 4, they are also very annoying to kill. You can also use it to block narrow paths or to give vision of an area for a short while.
 * Ability: Target Point
 * Damage Type: Piercing
 * Duration: 40
 * Ward HP: 75 / 200 / 325 / 450
 * Ward Damage: 10 / 19 / 29 / 38
 * Mana Cost: 20
 * Cooldown: 5

Poison Nova
Poison Nova makes a blast of venom around you, poisoning enemies caught by the cloud doing damage over time. At level 3 you can do up to 1215 damage to a group of enemies. One major thing to note about Poison Nova is that it can't bring an enemy's hp below 1. A fairly good secondary initiation spell that can really soften up the enemy team for your teammates to take down.
 * Ability: No Target
 * Damage Type: Magical
 * Radius: 830
 * Duration: 12 / 14 / 15
 * Damage: 36 / 58 / 81
 * Mana Cost: 200 / 300 / 400
 * Cooldown: 140 / 120 / 100
 * Scepter Duration: 14 / 15 / 16
 * Scepter Damage: 58 / 81 / 108
 * Scepter Cooldown: 140 / 120 / 60

Aghanim's Scepter can be bought by Venomancer and will increase the damage and duration of Poison Nova as well as reduce the cooldown of it at level 3.