Warlock

Demnok Lannik the Warlock is a ranged intelligence Hero and a very powerful support. His Shadow Word ability makes for an excellent heal as well as a decent harassment tool, and his physical attack helps him to ward off any enemies and keep his friends safe. He also possesses an considerable presence in team fights, as most of his abilities cover up a rather large area of effect.

Tips

 * Warlock is one of the best babysitters in Dota 2. Shadow Word allows him to heal his lane partner and Upheaval slows down enemies giving your partner a chance to escape or gank. Try to lane with carry heroes such as Spectre, or Phantom Assassin to boost their early-game.
 * Consider going solo lane if your team wants to try an early push strategy. Warlock's attack range, projectile speed, and damage allows him to farm nicely against other solo heroes.
 * Shadow Word can also be used as a harassing tool. Cast it on your opponent and keep hitting him whenever it's possible. Make sure you don't get hit by creeps too much while doing so.
 * Fatal Bonds is an immensely useful spell which amplifies your team's damage output. Bond 5 enemies together, and if they are all hit by a single area of effect spell or attack, the total damage will be doubled, since everyone of them will suffer 5x20% extra damage echoed from others.
 * You can use Upheaval to prevent wounded enemies from escaping. This is especially useful if used right after an AoE spell, such as your Chaotic Offering. Let your golem or your teammates finish the job.
 * If an ally is being chased, use your Upheaval from a distance to let him escape. Since the slow will last for some seconds after you stop channeling, you will also have time to fall back.
 * Initiate team fights by casting Fatal Bonds, followed by Chaotic Offering.
 * Use your golem summoned by Chaotic Offering to push towers, clear creep waves, attack weaker enemies during teamfights.
 * You can heal the golem with your Shadow Word to increase his tankiness.
 * Do not attack fleeing enemies with your golem, it will slow you down. Just keep the golem running close to them and let the immolation do the work for you.
 * Do not let your golem die needlessly to heroes, it will feed them experience and gold. If it's the last remaining unit for your team in a fight, have it run unless you can ensure a kill. Having it suicide into a nearby creep camps or even lane creeps/towers is better than allowing an enemy hero to claim the gold bounty of your golem, especially if you have two or more.
 * Although both Refresher Orb and Aghanim's Scepter allow you to summon two golems, Refresher Orb allows you to summon two full strength golems and utilize two seconds of AoE stun, but will cost a lot of mana to pull off, while Aghanim's Scepter is easier and cheaper to build and gives nice stats. This makes the Scepter the better choice for an early luxury item or a late-game item as a hard-supporter.

Trivia

 * In DotA, Warlock's ultimate is named Rain of Chaos and the summoned unit is called Infernal - the demonic mechanical in Warcraft universe. Both names were changed in the transition to Dota 2 to avoid copyright conflict.
 * In DotA, Warlock's Golem has green colored flames.
 * Warlock is related to Disruptor and Axe, as he comes from the Oglodi tribe.