Outworld Destroyer

Harbinger the Outworld Devourer is a ranged intelligence hero who qualifies as a carry, though unlike traditional carries, he excels against high-armor targets whilst being crippled by magic immunity. With Arcane Orb, his damage output is reliant on his intelligence attribute and the size of his mana pool, so he must focus more or less exclusively on items which augment them. Though he lacks somewhat in range and has no innate mobility skills, Arcane Orb deals Pure damage, meaning that if he gains an advantage in a match he deals constant, colossal damage which cannot be decreased or resisted except with total magic immunity. He and his allies enjoy more-or-less unlimited mana because of his Essence Aura, which gives them a chance to replenish a persentage of their mana upon casting a spell. With Astral Imprisonment, Harbinger can render himself or an ally invulnerable for a short period of time, or disable (and steal Intelligence from) the target enemy. His ultimate, Sanity's Eclipse, can instantly deal colossal area-of-effect damage against his enemies based on how much greater his intelligence is than theirs.

Tips

 * One of Harbinger's significant weaknesses is his fragility. Avoid taking in too much damage; if so, you will miss out on potential gold and experience, as well as put your team in danger by not dealing the needed extra damage against your enemies. Try to fight in the sidelines, or when your enemies are too busy to attack you. His defense can be boosted through items, but make sure not to deprive him of too much intelligence.
 * Try to level up as much as possible in the early stages of the game, be it from farming or killing other heroes. The more you advance in level, the more Intelligence and gold you will receive. The more Intelligence and gold you receive, the better you will dominate in the mid and later game. OD is extremely powerful in the later game, provided he farms well in the laning phase.
 * Level up Harbinger's Essence Aura fairly quickly so that he can solve his mana problems. Essence Aura can also make a good support ability for your allies, especially if they rely heavily on casting spells.
 * Astral Imprisonment is Harbinger's disabling ability, and can be used in numerous ways:
 * Early in the game, it can be used to harass against heroes you are laning against. It is easiest to land against melee heroes, but effective against most heroes (though sometimes for differing reasons.)
 * Strength and Agility heroes are good 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 three to five times depending on its level, stealing a total of 12/18/32/50 intelligence).
 * Intelligence heroes, on the other hand, lose damage as well as have their mana pool lowered, while Harbinger increases his. Harbringer's base attack damage will also increase by a good amount if you use Astral Imprisonment a few times, which makes last hitting in the mid lane very easy against some heroes.
 * It can be used to delay enemy heroes you are laning against, preventing them from getting a last-hit or deny.
 * It 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' spells, 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 abilities.
 * 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. Proper warding (by team mates) and map awareness are key.
 * In team fights, Astral Imprisonment can be used to shut down a key enemy character, such as a durable carry like Wraith King, so your team can focus on squishier supports. As Sanity's Eclipse can be used on imprisoned enemies, it may be preferable to initiate by imprisoning and immediately ulting the same target.
 * Other intelligence heroes, most notably and  Pugna, can render Sanity's Eclipse useless because of their rapid intelligence growth. Instead, focus on using your ultimate against other heroes whose main attribute isn't intelligence.
 * Use Astral Imprisonment to block yourself (or an ally) from spells; slow-moving projectile spells like 's Homing Missile or Sven's Storm Hammer give you plenty of time to block them. Lethal spells like  Sand King's Epicenter or even  Lion's Finger of Death can be rendered useless with good timing. Spells that cripple your movement and make you vulnerable for attack, like 's Kinetic Field,  Naga Siren's Ensnare, or  Chen's Penitence, can be decreased in time thanks to Astral Imprisonment's 1/2/3/4-second invulnerability period.
 * 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  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. As well, the pure damage goes through his Spell Shield.
 * However, in certain situations when Outworld Devourer is silenced or stunned for an extended period of time, Anti-Mage's and, especially  in combination with  and other heroes with mana drain like  Nyx Assassin, can still use Outworld Devourer's massive mana pool against him.

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, the Destroyer.
 * Outworld Devourer's original Dota 2 name was "Outworld Destroyer". This was changed to "Outworld Demolisher" on the Test Client, but due to community outcry, it was changed again when it arrived on the main client to his current name, "Outworld Devourer". Due to such name changes, there are many community humour names in circulation, such as "Outworld Developer".
 * Outworld Devourer has lines for carrying two even three Aghanim's Scepter. The reason for this is because in Dota 1 early development Aghanim's Scepter was made using Mystic Staff and a Soul Booster giving 500 mana and 30 int, which helped Outworld Devourer tremendously.