Arcane Warrior

Arcane warriors in Thedas
The arcane warriors once widely existed amongst the ancient Elves. However, after their fall, the art of the Arcane Warriors is seemingly all but lost.

Unlocking
This specialization can be unlocked while doing the Nature of the Beast quest line.

Location: Brecilian Ruins

Floor: Lower Ruins

Map: Middle Right; left section of two outstretching quarters.

Landmark: Broken Stone Altar; the section looks like a ruined library with a broken altar. If you see this land mark and it specifically says "Broken Stone Altar", then you are in the correct room.

Position: It is hidden in the shadows of that room; it's not sparkling, so just use your controller on the area across from the broken altar, next to the headless statue if you are playing on a console. If you are playing on PC press Tab to highlight all interactable objects in the room.

Item: Phylactery. When you touch it you experience the memories of the last elven arcane warrior who has remained trapped inside of the phylactery for centuries. He offers to teach you the secrets of the Arcane Warriors in exchange for setting his spirit free by placing the phylactery on an ancient altar. While the spirit of the elf has been imprisoned for so long that it forgets where the altar is located, the altar is actually right beside the phylactery. By destroying the phylactery, you unlock the Arcane Warrior specialization for the mage. In addition you receive 250 XP and  from Alistair.

Mechanics and tactics
In all cases having an Arcane Warrior in your group gives you a lot of added flexibility, and removes to a certain extent the need to have a second warrior character with you for the purposes of soaking damage when fighting large groups of enemies. The key to Arcane Warrior mechanics lies in two trade offs, one defensive between armor and fatigue, the other offensive between sword or staff, and mana managing.

Defensive
For the first, having the ability to wear the armor, which you acquire as soon as you get the Combat Magic ability, does not remove the associated fatigue increases on the mana cost of spells, and so heavy armor limits how many spells your character can use. Note that fatigue penalties also cause potions to become less useful, and you will lose significant amounts of combat time and damage output by relying on them.

Offensive
The second trade-off is offensive, between sword, the preferred weapon for close-up combat, and staff; this affects which spells you can cast. Going the sword route is possible, but if you try to cast spells for which the sword must be sheathed, your character will sheathe the sword, then cast. This causes a mid-combat delay which can cause a significant amount of trouble. By pausing the game and using the weapon-switch ability you can avoid the time penalty (weapon switch becomes instant in this case) and so micromanage your way around this. You can also add the weapon set to a hot key and swap your weapon set that way. That is also instant and has the added benefit that you can map your spells to the weapons you have in hand. So with your sword and shield, you will have drawn spells in your quick keys, but with your staff you will have your empty hand spells. This gives you a total of 10 spells across both weapons slots. However that requires a significant amount of player involvement if you use the radial dial. See Arcane Warrior Spellcasting for a complete list of spells that can be cast with a sword in hand.

Sustained abilities and mana
Arcane Warriors can use their sustained abilities to get very high levels of defense/armor/spell resistance. This can be powerful, but can limit what the Arcane Warrior can do to basically being an auto-attacking machine with decent damage and great defense. The various sustained Arcane Warrior abilities tend to have very heavy mana cost, and so a common tactic is to leave them off until you are low on mana. This allows you to open a fight with heavy area damage like Fireball and expensive crowd-control spells, and since casting a sustained ability does not cost you mana if your max mana is low enough, it is essentially free. At what point you switch is down to personal preference - the longer you leave it, the more flexible your casting options are. Nevertheless the Arcane Warrior as a melee fighter is a good way to extend a fight, giving you a little extra durability when you need it (much like Shapeshifter's Bear form ability). The small delay while you turn on your abilities does not usually matter much.

Play styles
Players have adopted three main styles for Arcane Warriors: Mage, Tank, & Hybrid.

Mage style
The Mage style Arcane Warrior remains primarily a ranged attacker with a decent mana pool; they rely primarily on lighter armor (fatigue < 15%) for defense and a staff as a weapon. Since they are more robust than standard mages, they can lead from the front or double as an alternate tank; however, they are not meant to be a warrior replacement. Since Shimmering Shield does not require Combat Magic to be active, they can stick with standard Mage Armor, along with mana regen gear, and use Shimmering Shield for the resistances and armor bonus. (Reminder: be careful not to boost resistances unnecessarily high: elemental resistances cap at 75%; spell resistance caps at 100%, while mental & physical resistances have caps at 100.)

Tank style
Arcane Warriors can be setup to tank every bit as well as a warrior, if not better. The ability to wear heavy armor and manage fatigue makes this caster extremely tough, at the expense of a weaker mana pool. This also makes it tougher to maintain aggro on opponents, as it' hard to keep dealing damage after when mana runs out in 4-5 spells. With the Combat Magic spell active, melee weapons use Magic instead of Strength to determine damage, so hits can pack some real punch. The downside is that a typical Mage character usually has an undeveloped Constitution and can not take a whole lot of damage. One remedy would be to take advantage of the specialization's strong defensive spells in conjunction with regular defensive mage spells. By activating shimmering shield, rock armor, combat magic, arcane shield, miasma and other buffs, the character can be made almost invincible. However, there are two noticeable disadvantages with this method: First, the character will be essentially limited only to basic attacks, with the slight possibility of casting a low level spell depending on willpower. Secondly, the vast amount of buffs used in unison can make the game very prone to crashing, even on a console.

Hybrid style
The hybrid style attempts to combine the best of the Mage and Tank styles. The Arcane Warrior primarily relies on getting close to the enemy and using short range spells to help manage opponents, especially Cone of Cold and other snares. The primary weapon is a sword; keep in mind which spells work best with this type of weapon and swap in a staff during combat when sensible. Another form of hybrid is sustained ability overload. keeping active defense spells like rock armor spell shield and arcane shield, and also keeping active frost/fire weapons combat magic and telekinetic weapons for both a good offense and an almost impenatrable defense. this of coure renders the arcane warrior melee instead of spells. the main spell used (that isnt sustained) would probably be a blood magic spell or Arcane Bolt. in this case its almost essential to have the arcane warrior be a tank and have maybe 2 other DPS and one healer.

Blood mage
Blood mage is a popular second specialization choice for an Arcane Warrior because it can help to offset the disadvantages of a low mana pool at the cost of health by allowing the Arcane Warrior to cast Blood Magic spells using health as mana. Presumably the heavy armor will give the Arcane Warrior enough headroom on health to do this, although a reasonable constitution would be highly recommended. The effective Blood Wound spell can also be acquired, which is an ideal choice for a more offensive Arcane Warrior. This would be the recommended combination for the 'gish' build mentioned above.

Spirit healer
The other main choice, spirit healer, producing a mixed character with offensive and defensive magic and good durability. This combination works best with no more than medium armor, since a decent amount of mana is needed to power the high-level healing spells. Also worth noting is that Cleansing Aura can draw as much aggro as a Warrior with Threaten.

Shapeshifter
Shapeshifter is an interesting combination but unpopular choice with Arcane Warrior. There is a fair bit of redundant overlap between the two, as they both offer exclusive options in melee, but a foremost Shapeshifter with secondary Arcane Warrior can use massive armor and Bear Shape and be incredibly hard to kill with weapons. The main problem with this is the fact that Shapeshifter overall does very poor damage because of the fact that, unlike what the tooltip for Shapeshifter says, it does not actually use magic to calculate damage.

Battlemage
Battlemage is an especially potent combo of subclasses as you can use the buffs and spells from the Battle Mage and go straight into the thick of combat wearing heavy and massive armor. This has drawbacks however, do not expect to be able to cast ANY spells except buffs, and it limits your ability for area of effect (AoE) spell use, as you might not like getting hit by your own spells. But the advantages outweigh the drawbacks significantly, use flame or frost weapon with elemental mastery and elemental chaos active as well as mage armor and shimmering shield and you get a very high DPS and defense

Weapons
Currently there is only one arcane warrior specialization specific item in the game:
 * Spellweaver

Equipment
Carefully kit your arcane warrior with appropriate bonuses, especially mana and/or stamina regeneration.
 * Stamina: Executioner's Helm, Eamon's Shield. The Item Sets from Return to Ostagar like Cailan's Armor and Cailan's Arms both have set bonus for Stamina regeneration. The Warden Tower Shield and Warden Commander Armor Set from Warden's Keep have a bonus to Stamina and will work great for an Arcane Warrior.
 * It is possible to completely offset Shimmering Shield's -10 penalty to Combat Mana Regeneration if you choose the correct equipment. Combine any of Wade's Superior Dragon Armor Sets (+2 regen) and Andruil's Blessing (+2 regen) with Cailan's Arms (+5.5). On Xbox and PS3, you have more weapon/shield options, as the regen amounts are higher on each piece.

Reference
Dragon Age: Origins - PRIMA Official Strategy Guide.