Warlock

Mechanics

Warlocks have relatively low AoE damage but are one of the best single target damage classes in the game

Warlocks are the personification of a glass cannon, sacrificing their own health to deal significant damage. This can be offset with the correct use of Twisted Font, which is a 'mana shield', absorbing damage at the cost of the players mana. The man you then loose is replenished through the application of Sadism.
Warlocks also bring with them a damage buff to all other casters, whereby their Curse causes the target to suffer 10% additional magic damage.

Attribute points should be spent in approximately a 1 Strength : 4 Intelligence ratio.

Ultimately you want ~750 base Strength and ~2750 base Intelligence in order to achieve 20-25,000 health, Agility and Attack Speed are negligible on a Warlock.

For your familiar skills, you want to invest in the 5% Spell Power buff from Aptitude and your preference of 75 Strength/Intelligence from Gift of Endurance/Wisdom, to achieve the Strength breakpoint above.

At max level, the core setup is / , combined with your choice of Olympian Relic;

Immortal Armor of Hepheastus - This Relic offers survivability, mana regeneration and spell power. Easily the best choice to pull you through the difficult fights when you don't have a dedicated Tank
Searing Flame of Prometheus - Searing Flame provides the best damage output but sacrifices survivability

>>Blanket Disclaimer: You, and every other player will need items from all crafting professions so there is no 'best' profession for any given class. If you are selfishly looking for personal enhancements, Alchemy is the only profession whereby you can't bring items you crafted through to another game, so this might be the best choice on a personal level, but increases dependency on others for crafting<<

Abilities

Sadism

You gain a Sadism stack whenever a Tormented enemy dies. Then become Sadistic for the next 8 seconds if you were not already. When Sadism naturally times out, you recover mana equal to the number of stacks; 1 stack: 4% maximum mana. 2 stacks: 8% maximum mana. 3 stacks: 16% maximum mana. 4 stacks: 32% maximum mana. You can have up to four stacks active at one time. 12 second cooldown.

Curse (T)

Place a demonic curse upon a target enemy causing it to suffer 10% more magical damage from all sources for 20 seconds. Costs 10% maximum health. 60 second cooldown.

Items

While leveling, your priority will be as follows:

Levels 1-50

Level 7

You can upgrade your skills to level 2 at the Book shop in Athens

Level 10

You can now get an additional class skill, Curse, which can be dropped from Atlas, Thea or Uranus.

Level 15

You can upgrade your skills to level 3 at the Book shop. Additionally, now would be a good time to hunt for some Oracle's Set pieces / , dropped by Rokthul or crafted through professions.

Level 30

You can upgrade your skills to level 4 at the Book shop.
Additionally, you can now access the High Oracle's Set / from Manticor, Goretusk, Gethos, or crafted through professions, and Class set items.

Your Class set is made up of 3 items, Robes of Shadows and Staff of Shadows have a chance to be dropped from the 3rd through 6th titans (Themis, Cronus, Uranus, Rhea), and from Pelias. Pendant of Shadows is crafted at Master Metalsmith Heletes, costing 1 Blood Ruby and 1 Lump of Pure Adamantium.

When you have all 3 items in your inventory, you will gain Shadows Set— Whenever you cast a spell you have a 15% chance to increase your Spell Damage by 50% for 20 seconds.

Level 40

Now you're level 40, Eris' Golden Apple of Discord will be a good upgrade, and its use effect can be used from your familiar when you out grow it later! Eris' Golden Apple of Discord can be dropped from Occeanus, Gaea or Heiros.

If you're struggling, you can also search out the Regal Crown and Crystal Helm from Cyclopse.

Level 45

You can now get the final Delphi Oracle's Set / from Heiros or crafted through professions.

You can now upgrade your Regal Crown and Crystal Helm to a Regal Helm of Sparkling Crystal at Metalsmith Arcadios in New Issus if you managed to acquire them.

Level 50

You can upgrade your skills to level 5 at the Book shop.

Another good item you can pickup now would be Priams Scepter from Aeacus. Even if this item isn't a big upgrade on what you have, it is worth getting as it can be upgraded later on.

Torment (Q)

Level 1

Inflict a target enemy with excruciating pain causing it to suffer 100 (+1.0 spell damage) magical damage over 5 seconds. Torment stacks up to three times and refreshes the duration of active stacks (personal). Costs 2.5% current health. 1 second cooldown.

Twisted Font (W)

Level 1

For the next 8 seconds and damage received (including spell costs) is delt to your mana instead of your health. Every point of damage taken while Twisted Font is active costs 1.35 mana. 18 second cooldown.

Death Wave (E)

Level 1

Unleash a wave of death at a target location dealing 50 (+1.0 Spell Damage) magical damage in its wake, and then bursts into a nova dealing 1.0 spell damage magical damage in a 650 AoE. Costs 7.5% current health. 10 second cooldown.

Vengeance (R)

Level 1

Blast a target enemy with a burst of agony dealing 100 (+1.0 Spell Damage) magical damage and Stifle I the target for 3 seconds, reducing its movement speed by 20%. Costs 5% current health. 5 second cooldown.