The Necromancer
This profession guide is accurate as of BWE2.
A necromancer is a practitioner of the dark arts who summons the dead, wields the power of lost souls, and literally sucks the lifeblood of the enemy. A necromancer feeds on life force, which he can use to bring allies back from the brink or cheat death itself.
-Official Guild Wars 2 Website

Overall Theme
The necromancer is a bit harder to pin down with one theme than other classes. But, in the end, it all boils down to corruption. The necromancer can raise undead minions out of the ground, and it can steal life from its enemies. However, the necromancer specializes in converting boons and conditions on allies and enemies to be able to change the tide of the battle and maintain the upper hand. As part of their attacks, they generate Life Force, their unique resource. It’s used to activate and fuel Death Shroud, a powerful form with powerful skills. While in death shroud, necromancers take damage to their accumulated Life Force rather than their own health. Many of the necromancers abilities create marks, AoE’s that require a trigger for their affect much like extra-large traps.
Weapons
Staff – The staff is completely AoE. The auto-attack, Necrotic Graps, is a line AoE attack. The rest of the abilities are all marks like Chilblains.
Axe (MH) – The axe is a fairly nondescript mid-range weapon. Worth noting, however, is the Life Force generation possible with Ghastly Claws.
Dagger (MH) – The main-hand dagger is the only melee weapon necromancers have. Along with its immobilize, it also has Life Siphon to siphon life from your foes.
Scepter – The scepter is the long-range weapon for condition-based fighting. Its auto-attack causes bleeding and poison and it also has an AoE cripple. Additionally, Feast of Corruption relies on conditions for generating life force.
Dagger (OH) – The off-hand dagger is a perfect weapon that is well suited to surviving foes. Beyond just blindness and weakness, you can also give your opponents your conditions with Deathly Swarm.
Focus – The focus is a good offensive weapon that focuses on debilitating your opponent. Spinal Shivers is an extremely powerful skill that removes boons as well as chills your enemy.
Warhorn – The warhorn is useful in both offensive and defensive situations. While it can be used to keep foes in range, Locust Swarm is also handy for escaping from melee enemies.
Underwater
Spear – The spear is an AoE-based melee weapon underwater that applies that AoE and conditions for skills like Wicked Spiral. You can also keep foes in range well with skills like Deadly Catch.
Trident – The trident is a more long-range, single-target focused weapon that works more heavily with conditions. Crimson Tide, the auto-attack, applies a five-second bleed with each attack. Sinking Tomb is also incredibly useful, as sink skills aren’t the most common in GW2.

Slot Skills
Many of the necromancer’s slot skills take the same condition-and-boon based approach of the rest of the profession, with the addition of minions. When it comes to healing skills, all of them are viable options. Well of Blood is the obvious go-to for party situations, while Consume Conditions offers the highest healing potential over any amount of time.
Corruption – All four of the corruptions are reminiscent of the sacrifice skills from the original profession in GW. You inflict a condition on yourself in order to inflict a much more powerful effect on your opponent.
Minion – The minion skills all summon a minion (or two for Summon Bone Minions) out of the ground without requiring any corpse. Once summoned, each skill has a toggle with various different effects. Other than the bone minions, the toggle skill leaves the minion alive.
Signet – As with all signets, each skill has a passive effect that can be put on recharge for its activated effect. The signets focus on conditions, stealing health, and life force.
Spectral – The spectral skills are are really a group of miscellaneous effects that don’t actually have a common factor.
Well – The wells are all self-centered AoE’s that pulse a condition-based effect every two seconds.
Elite – The necromancer has two different form elite skills. Plague turns you into a condition-causing cloud, while Lich Form turns you into a lich with strong skills matching the rest of the necromancer’s skills. Summon Flesh Golem summons the strongest minion of all that cripples with each attack.

Traits
The necromancer’s five traits are mostly named after the necromancer’s attributes from the original Guild Wars. The last line is linked to the attribute, Hunger, which increases the size of the Life Force pool.
Spite (Pow/Exp) – The minor traits heal on kill, buff healing, and give might when hit at low health. The major traits buff signets, increase minion damage, remove conditions with ills, add ways of gaining might, increase axe damage, buff marks, add retaliation to Death Shroud, and auto-cast Spinal Shivers on enemies you put below 25 percent health. The final traits are Axe Training and Chill of Death.
Curses (Pre/Mal) – The minor traits cause bleeding on crits, give add fury to Death Shroud, and add damage for conditionso n foes. The major traits buff criticals, lengthen bleeds, buff many conditions, reduce corruption recharges, lengthen spectral durations, add damage to fear, give ground-targeting to wells, and reduce warhorn recharges. The final traits are Lingering Curse and Withering Precision.
Death Magic (Tou/Con) – The minor traits add a chance to summon a minion on kill, buff toughness with minions, and buff power. The major trats buff minions, buff marks, add protection to wells, auto-cast Spinal Shivers when entering Death Shroud, make marks unbockable, reduce staff skill recharges, give armor while channeling, and increase damage to low-health foes. The final traits are Death Nova and Necromatic Corruption.
Blood Magic (Vit/Com) – The minor traits add regeneration when brought to 90 percent, siphon health on every hit, and buff power with high health. The major traits add siphoning to many skills, buff siphoning, reduce dagger recharges, add healing to Death Shroud, increase movement speed with daggers, buff minions, buff wells, drop a Well of Blood when reviving, and drop a Mark of Blood on dodge. The final traits are Fetid Consumption and Vampiric Rituals.
Soul Reaping (Pro/Hun) – The minor traits increase Life Force gain, auto-cast Spectral Armor at half-health, and buff power with Life Force. The major traits fear enemies when downed, add Reaper’s Mark when reviving, reduce spectral recharges, buff Death Shroud, lengthen fear, add Life Force to marks, and auto-cast Locust Swarm when brought to 25 percent. The final traits are Foot in the Grave and Near to Death.

Difficulty
Necromancers are fairly average in terms of difficulty. They’re easy to pick up and play, but take a little more to actually find something that works well. They’re a fairly middle-ground class in terms of difficulty.