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 a 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 laning partners in Dota 2. Shadow Word allows him to heal his lane partner and Upheaval slows down his enemies, giving your partner a chance to escape or gank. Try to lane with the Carry heroes of your team, so that they can reach their potential sooner.
 * Warlock's attack range, projectile speed, and damage allows him to farm nicely against other solo heroes. As well, the head-start in levels can give him his golem sooner, so that he can push earlier into the game.
 * Shadow Word makes a great harassing skill. When your enemy is under its effect, try adding more damage to it by auto-attacking them.
 * Fatal Bonds is an immensely useful spell which amplifies your team's damage output. Try to bond as much enemies as possible to enlarge the damage output.
 * You can use Upheaval to prevent wounded enemies from escaping. This is especially useful if used right after an area-of-effect spell, such as your Chaotic Offering. Let your golem or your teammates finish the job.
 * If an ally is being chased, use your Upheaval to cripple their chasers. Since the slow will last for some seconds after you stop channeling, you will also have time to fall back.
 * When initiating, make sure to cast Fatal Bonds first, then Chaotic Offering; this way, you can output more damage against all your targets.
 * Your golem is tanky; when possible, use it to tank creeps or towers, so that you can dispose of them sooner.
 * When chasing fleeing heroes with your golem, don't stop to auto-attack them, since it will slow the golem down. Instead, keep it moving with the heroes, so that the Permanent Immolation can do its damage.
 * Do not let the golem die needlessly to your enemy heroes, since its gold bounty is quite high. If it's the last remaining unit for your team in a fight, have it flee unless you can ensure a kill. Having it die against creeps or towers is better than allowing an enemy hero to claim the gold bounty of your golem. Having two golems from Aghanim's Scepter will cut the bounty of each golem in half.
 * When looking to summon more than one golem in the battlefield, it is usually better to go with Aghanim's Scepter instead of Refresher Orb. Though the Scepter will give you slightly weaker golems, the item itself is cheaper and will bulk your attributes up, as well as provide two golems instantly. Refesher Orb is more expensive, and summoning two golems can deplete most of your mana. As well, there's a slight delay in summoning them.
 * The best solution is to acquire both of these items, as it will provide you with a total of four golems at your disposal.

Trivia

 * In DotA, Warlock's ultimate is named Rain of Chaos and the summoned unit was called an Infernal, a hulking golem with green-colored flames. Both names were changed in the transition to Dota 2 to avoid copyright conflict.
 * Warlock is related to Disruptor and  Axe, as he comes from the Oglodi tribe.