Dota 2/Ostarion the Wraith King

Wraith King is a melee Strength hero that is considered one of the simpler characters in the game, with only one active ability. However, he is still a very solid and fun hard carry, and one that is very difficult to kill. His Vampiric Aura and Reincarnation abilities gives Wraith King amazing survivability, and his Wraithfire Blast and Critical Strike lets him disable and rack up the damage. Wraith King might look like the easiest hero to play in the game, but he can also be one of the toughest.

Wraithfire Blast
Wraithfire Blast is Wraith King's only active ability. He fires a ball of wraithfire that stuns the targeted unit on hit, then slows them and deals damage over time. Use this to initiate a kill, slow down pursuing enemies as well as disabling key heroes. You can also use it for harssment but the mana cost will be too high during the early game for it to be very useful.
 * Ability: Target Unit
 * Affects: Enemy Heroes
 * Damage Type: Magical
 * Damage: 50 / 100 / 150 / 200
 * Stun Duration: 2
 * Slow: 20%
 * Damage Over Time: 15 / 30 / 45 / 60
 * Slow Duration: 2
 * Mana Cost: 140
 * Cooldown: 8

Vampiric Aura
Vampiris Aura grants lifesteal for all units in a 900 radius area of effect. At level 4 it gives you and your allies 30% lifesteal. For comparison, Satanic only grants a 25% lifesteal for the user, making Vampiric Aura the best passive lifesteal ability. Additionally, it is fully stackable with lifesteal-granting items and unique attack modifiers like the Mask of Madness and Broodmother's Insatiable Hunger.
 * Ability: Passive, Aura
 * Affects: Allies
 * Lifesteal: 15% / 20% / 25% / 30%

Mortal Strike
Mortal Strike simply gives you a chance to do extra damage. Although it doesn't have the best activation chance or bonus damage, it still gives you a nice boost to your damage output.
 * Ability: Target Unit, Passive
 * Critical Damage: 125% / 175% / 225% / 275%
 * Critical Chance: 15%
 * HP Drain: 20%
 * Drain Duration: 7
 * Mana Cost: 30
 * Cooldown: 25

Reincarnation
Reincarnation lets Skeleton King revive himself when he dies, regaining all of his hp and mana as well as slowing enemies near him by 50% for 4 seconds upon death. This ability will activate even when you're Silenced, as long as you have enough mana and the ability is not in cooldown. This is why Wraith King is so hard to kill. Being able to revive himself every minute makes him even more durable. The mana cost is also relatively cheap for such a powerful ability, only using up as much mana as a Wraithfire Blast.
 * Ability: Passive
 * Reincarnation Time: 3
 * Mana Cost: 140
 * Cooldown: 260 / 160 / 60