From Flagship Wiki

The Guardian is the tank of Hellgate. Since they have the highest armor in the game, thanks to the fact that they wield a high-armor shield and sword combo, they’ll take a lot less damage in combat than their compatriots, making them handy in any kind of multiplayer game. They don’t skimp on the damage, either, making them effective soloers.

[edit] Equipment

The best sword and the best shield you can get are the order of the day here. You’ll want a variety of damage types and weapon speeds in your equipment sets characters that focus on Sword of Reckoning for massive damage will want to find the slowest, highest-attack sword they can get. If you’re focusing on shield bashing, though, you may want to try and get a few different shields with different damage types, making sure that you have a good fire-based shield for Igniting tough enemies.

When it comes to armor, you’ll be more likely to want items with high armor ratings rather than high shields. Since you’re going to be in the thick of things, and your auras will require you to be surrounded by foes, your shields will usually drop fairly quickly, whereas your armor will always be present and helping to mitigate damage.

[edit] Skills

Aura of Renewal will be your best friend at the earlier levels, as it will let you recharge a good amount of your health when surrounded by enemies. Sure, they’ll hit you, but if you load up on armor, you should be able to regenerate just as much if not more health than they can dish out. Later on, you may want to shift to Aura of Power and use Prayer of Healing or Health Injectors when you run low on health.

Tip: The high damage output of the Anchor skill can make some alternate builds possible here. Some players like to keep a high-damage splash weapon, like a rocket launcher, in one of their equipment slots and use it with the Anchor ability, or even forgo shields and swords altogether for guns. Mix in Aura of Deflection or Vengeance to reflect other ranged attacks, and you’re money.

Apart from the myriad defensive and taunting skills, you won’t have a huge amount of offensive skills at your beck and call. Sword of Reckoning is great for quickly bursting down against a tough boss enemy, while Anchor will let you sit still and deal a lot more damage to enemies that are willing to come to you - combine this with Challenge to ensure that everyone gets a taste.

Since you’re going to be using a shield for most of the game, though, you’ll probably want to invest in the Shield Bash tree of skills. Although shields won’t deal as much damage as your swords likely will, they can still be incredibly useful when combined with these skills, especially Shield Turn, which will strike all enemies nearby and increase your chance to inflict a status effect on your foe. While most early shields will deal physical damage (and thus stun your foes), you will eventually start finding shields that deal other sorts of damage, such as spectral and fire. It’s quite fun to spin around and ignite all of the enemies that surround you, then watch them burn up without having to attack them personally. Bosses can fall to these attacks, as well; just find a good fire shield and spam Shield Bash at them until they catch on fire.