Khaos Champion

Mechanics

Khaos Champions are decent AoE tanks, with great utility; Grave Seize not only taunts, but drags the target to you, Decimate reduces enemies damage by 10% in an AoE, and deals reasonable AoE damage with Requiem and Dies Irae.

Attribute points should be spent in approximately a 5 Strength : 2 Agility ratio initially to build attack speed. Once you have ~200 base Agility you can devote all your remaining attribute points into Strength exclusively.

For your familiar skills, you want to invest in the 5% Increased Health from Vigorous and of 75 Strength/Agility from Gift of Dexterity / Endurance, ensuring you don't exceed 400 total Agility / Attack Speed.

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

Towering Shield of Athena - Objectively best, incredible damage mitigation with a little bit of extra damage from the Strength, AoE armor buff, and a on-use effect to fully heal and replenish the mana of yourself, and all nearby players. Extremely useful for when the healer is OOM!
Ares' Bloodthirsty Spear - Good damage and can further supplement damage using Ares' Sword of Command on your familiar. Used right, the regeneration from this item can provide personal survivability similar to that of Towering Shield of Athena while producing significantly more damage. However, you loose the group buffs and on-use group heal. That said, this is an excellent option if you prefer a Damage or off-Tank role!
Thundering Hammer of Zeus - If no-one else in the group has a Hammer of Zeus, this will outperform Ares' spear if not combining the effects of Ares' Sword of Command on your familiar. Further, not only is your damage higher, but you also give a group damage buff and reduce your targets armor to increase over-all damage done. If however someone else in your group is using Hammer of Zeus as Clerics commonly do, you will have significantly better output using Ares' Bloodthirsty Spear as the damage aura does not stack.

>>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

Unbridled Khaos

Whenever you land a successful auto-attack; You have a 10% chance to deal additional base auto-attack damage, triggering on-hit effects. Then, gain a Shroud stack. 1 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, Dies Irae, 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 Spartan Field 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 Spartan War Set / from Manticor, Goretusk, Gethos, or crafted through professions, and Class set items.

Your Class set is made up of 3 items, Khaos Shield and Khaos Blade have a chance to be dropped from the 3rd through 6th titans (Themis, Cronus, Uranus, Rhea), and from Nelus. The Khaos Helm 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 Khaos Set—Whenever you auto-attack, recover 2.0 Armor Damage Reduction(%) Health.

Level 40

Now you're level 40, Sword of Command will be a good upgrade, and is used later for other items. Sword of Command can be dropped from Occeanus or Gaea.

If you're struggling, you can also search out the Barbaric Helm from Cyclopse.

Level 45

You can now get the final Spartan Elite Set / from Heiros or crafted through professions.

Level 50

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

You can now upgrade your Barbaric Helm to a Savage Helm at Metalsmith Arcadios in New Issus if you managed to acquire it.

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

Shroud

Level 1

Effect One - Whenever you cast the following spells; Grave Seize: Gain three Shroud stacks. Decimate: Gain two Shroud stacks. An individual stack grants 1% damage reduction for 8 seconds. If an enemy attack you while Shroud is active: deal 1.0 Strength magical damage to the attacker. Then, consume a stack if none were consumed in the past 0.25 seconds. You can have up to six stacks active at one time. Effect two -- You have a base mana regeneration of 0.75 mana per second.

Grave Seize (Q)

Level 1

Deal 100 (+2.0 Strength) physical damage, and Stun the target for 1.5 seconds. Pull it towards you if the target isn't currently immune to Stun. Then, Taunt the target for 2.5 seconds. Costs 5 mana. 12 second cooldown.

Requiem (W)

Level 1

Traps restless souls in a vortex which deals 30 (+0.15 Strength) magical damage per second to enemies within a 200 AoE of the Khaos Champion. If an enemy dies inside Requiem, the duration of Requiem extends by one second. Lasts for 30 seconds. Costs 10 mana. 60 second cooldown.

Decimate (E)

Level 1

Decimate all enemies in a 300 AoE, reducing their auto-attack damage by 10% for 8 seconds. Costs 5 mana. 15 second cooldown.

Dies Irae (R)

Level 1

You unleash a chorus of six spirits towards target location. Whenever a spirit hits an enemy unit; The spirit dissipates, dealing 200 (+0.5 Strength) magical damage to the unit. Then, gain a Shroud stack. Costs 10 mana. 20 second cooldown.