Outworld Destroyer

Harbinger the Outworld Destroyer is the sole Intelligence hero who qualifies as a Hard Carry. His damage output is entirely reliant on his Intelligence stat and the size of his mana pool, so he must focus more or less exclusively on items which augment them. Though extremely fragile, he deals the greatest Pure damage in the game which increases with his mana pool. With sufficient gold advantage, he will deal constant, colossal damage which (because it is Pure damage) cannot be decreased or resisted. He and his allies enjoy more-or-less unlimited mana due to his aura, he can protect himself or an ally or disable (and steal Intelligence from) an enemy, and he can instantly deal colossal area damage with his ultimate. Few heroes are capable of putting out as much damage as a pumped up Outworld Destroyer. Due to his ability to constantly and limitlessly replenish his mana, he is arguably the only hero in the game who directly counters Anti-Mage.

Tips

 * Astral Imprisonment is a good harassment spell early game since you can steal intelligence from enemy heroes. This can be used to great effect against Strength or Agility based Heroes since their intelligence is fairly low, potentially lowering their maximum mana points to the point where they are unable to cast any spells. It can be twice as effective on Intelligence based Heroes because they also have damage stolen from them all the while Outworld Destroyer is increasing his own. Additionally, the Intelligence steal stacks (up to 5 times for 12 seconds at rank 4 for a total of 50 stolen Intelligence) if you cast it multiple times on the same enemy.
 * Another way to harass with Astral Imprisonment is whenever your lane creep is about to die and your enemy heroes want to kill it, banish him then deny that creep to halve the experience that hero should have gained regardless of being able to kill that creep or not.
 * Astral Imprisonment can be used strategically on yourself or allies to dodge an impending attack, wait out a dangerous effect on an enemy hero, or buy valuable time that may increase survival. Examples include: dodging Tinker's incoming Heat-Seeking Missile, avoid damage from Sand King's Epicenter and saving an ally who is being focused to death in a team fight as well as removing a threatening enemy hero to ensure escape into better positioning.
 * Astral Imprisonment should be used to reduce the Intelligence of enemy heroes and increase Outworld Destroyer's before using Sanity's Eclipse for maximum effect. The effective difference in Intelligence is doubled because enemy heroes lose Intelligence while Outworld Destroyer gains Intelligence. This is especially useful during the laning phases early in the game and can easily net a kill.
 * Because of its utility and versatility, Astral Imprisonment is recommended to be leveled before Arcane Orb as the Intelligence steal (including the bonus damage from Intelligence being the main attribute of Outworld Destroyer and increased effectiveness of Sanity's Eclipse) and survive-ability afforded by it outweigh Arcane Orb early on.
 * Purchasing items that increase your maximum mana or Intelligence will greatly increase the damage of your Arcane Orb and Sanity's Eclipse.
 * You should always use Sanity's Eclipse at the start of each combat since the mana burn (75%) is significant enough to shut down any nukers or supporters like most Intelligence heroes after they use 1-2 of their spells, while dealing some damage to soften the Strength and Agility heroes.
 * Unlike most auto-cast spells, Arcane Orb can be targeted by Pugna's Nether Ward. Use this ability sparingly when Pugna is about.
 * Arcane Orb does a major bonus damage (up to 400) to illusions: making Outworld Destroyer very effective against heroes like Phantom Lancer, Chaos Knight, and Naga Siren. Arcane Orb also deals huge bonus damage to most summoned units; easily wiping out units summoned by Enigma and Nature's Prophet averting their pushing strategies and netting easy gold.
 * Silencer is a highest threat against Outworld Destroyer; if Silencer's Intelligence surpasses Outworld Destroyer's, Sanity's Eclipse will have no effect against Silencer.

Trivia

 * Outworld Destroyer's original title was Obsidian Destroyer, a name that is similar to two units from Blizzard's Warcraft 3. Those two units are Obsidian Statue, which could permanently become a flying unit known as the Destroyer.