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 (rendered even more so by his inability to build any significant durability items), he deals Pure damage which increases with his mana pool, meaning that if he gains an advantage in a match he deals constant, colossal damage which (because it is Pure damage) cannot be decreased or resisted. He and his allies enjoy more-or-less unlimited mana because of 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. Because of 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 effectively against strength based heroes since their intelligence is fairly low, lowering their maximum mana points or intelligence based heroes to steal damage from them while adding to your own. Additionally, the intelligence steal stacks 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.
 * 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 significance 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 lot of bonus damage to illusions, which makes Outworld Destroyer very effective against heroes like Phantom Lancer, Chaos Knight, and Naga Siren.
 * Silencer is a highest threat against Outworld Destroyer, if Silencer's Intelligence can pass Outworld Destroyer the Sanity's Eclipse will be not effective 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.