Outworld Destroyer

Harbinger the Outworld Devourer is a ranged intelligence hero whose power is based almost entirely on its mana pool. Its skills increase in damage with the amount of mana and intelligence it has and with proper items can increase to extraordinary levels. As a hard carry, it becomes extremely powerful in the late game and can destroy enemies almost at once.

Though fragile (rendered even more so by the inefficieny of building durability items), its Arcane Orb deals Pure damage which cannot be resisted, and so it has colossal damage output in almost any situation. In addition, it and its allies enjoy more-or-less unlimited mana because of its Essence Aura, which gives a chance to replenish a quarter of total mana upon casting a spell. Astral Imprisonment gives Harbinger the ability to banish, taking enemy heroes out of combat and stealing intelligence or rending itself or allies or from harm's path. Its ultimate, Sanity's Eclipse, instantly deals devastating area-of-effect damage based upon how much greater its intelligence is than those of target enemy heroes.

Tips

 * Harbinger's biggest weaknesses is its fragility. Damage harms Harbinger in the early game such that a few spells mean it has to miss out on farm and other sources of potential gold and experience and team fight presence. Initially, Harbinger must fight from places where retreat is possible and the full force of the enemy team cannot come upon him, or when enemies are too preoccupied to attack.
 * If health is increased through items, try to include additional intelligence with it, or if not, make sure the item gives enough so that it does not constrain space in the inventory.
 * Try to level up as much as possible in the early stages of the game, be it from farming or emerging onto teamfights to last-hit other heroes. The more intelligence and gold received, the greater advantage Harbinger has over other heroes. The greater the advantage, the earlier Harbinger dominates battles and competes against other late-game carries.
 * Essence Aura is one of the best passives in the game, and all but ensures a friendly team has mana for spells. It makes him one of the more powerful carries alone and is powerful support for teammates. Early leveling of it can be quite useful.
 * Astral Imprisonment is Harbinger's disabling skill, and can be used in numerous ways:
 * Early in the game, it can be used to harass against heroes you are laning against.
 * Strength and Agility heroes are ideal targets, since Astral Imprisonment steals intelligence from their already low supply. They can repeatedly be disabled to the point that they are unable to cast spells (the steal stacks up to five times, stealing a total of 20/30/40/50 intelligence).
 * Intelligence heroes lose damage as well as have their mana pool lowered, while Harbinger increases his.
 * Astral Imprisonment can be used to delay enemy heroes you are laning against, giving you more time to either deny or last-hit creeps.
 * Astral Imprisonment can be used to dodge incoming spells when cast on yourself or allies; spells like Tinker's Heat-Seeking Missile, Sand King's Epicenter, or Sven's Storm Hammer can be rendered useless when under Astral Imprisonment.
 * Astral Imprisonment can also be used to buy time, be it escaping or trying to chase an enemy. While escaping, you can cast it on yourself or any dying ally to shift the enemy's focus away. While chasing, you can step ahead of the imprisoned enemy's path and make it harder for them to escape.
 * Use Astral Imprisonment carefully against your enemies when your allies are present in the team fight. Using it too much in these situations can potentially block your allies' skills, especially if they are channeling disables (i.e. Pudge's Dismember). Use it when your teammates are out of disables, or when the enemies are in the process of escaping. As well, try to target other units that are currently not disabled or crippled by your teammates.
 * Because of its utility, versatility, and intelligence steal, Astral Imprisonment is usually taken first before most other skills.
 * When Harbinger's Essence Aura is high enough (at least Level 3), you can keep casting Arcane Orb against enemy targets to restore his mana right away if depleted.
 * Casting Sanity's Eclipse can prove important when a team fight starts, since it can shut down spell-reliant casters by burning 75% of their mana, as well as soften strength and agility heroes. Keep in mind that your intelligence must be at least marginally higher than theirs so that the effects can work.
 * Outworld Devourer has no reliable escape until he gets a Force Staff. Frequent early ganks can put him at a severe disadvantage. Protection (laning with a support) is recommended.

Hero Tips

 * Other intelligence heroes, most notably Silencer and  Pugna, may be unaffected by Sanity's Eclipse, making it useless against. It should be targeted on their allies, and Harbinger should be prepared to engage them with other means.
 * Pugna's Nether Ward will count Arcane Orb as a spell cast, so make sure to destroy it before liberally using Arcane Orb against other enemy heroes.
 * Arcane Orb deals bonus damage against illusions, making it harder for illusion-reliant heroes like Phantom Lancer or  Chaos Knight to fight you. Summoned units also take additional damage, turning units like  Enigma's eidolons and  Nature's Prophet's treants into easy gold.
 * Outworld Devourer counters Anti-Mage, since he can regain mana instantly from Essence Aura just by auto-casting with Arcane Orb.

Trivia

 * Outworld Devourer was originally called Obsidian Destroyer in DotA. Obsidian Destroyer was based off of two units in Warcraft III: Frozen Throne; the Obsidian Statue, and its alternate form, Destroyer.