Guide to playing as an Assasin

Attributes
Shadow Arts
Shadow Arts mainly contains self-healing and defensive abilities and shadow steps. The currently most popular healing combination for assassins is Feigned Neutrality combined with Deadly Paradox. That way your attack skills are disabled, so you don't accidentally end Feigned Neutrality.

Deadly Arts
Deadly Arts is the assassin's damage source if not using daggers. There are simple damaging spells in here, as well as battle-enhancing hexes. The currently most frequently used Deadly Arts skills are Expose Defenses to counter blocking, Siphon Speed as a snare and cover hex and Augury of Death for a mostly unconditional Deep Wound.

Critical Strikes
Critical Strikes represent the assassin's energy management. For every critical hit, the assassin gains energy, from 0 to 3. In addition to the energy gain, the chance for a critical hit on an attack is increased by 1% for each rank in this attribute. Refer to the table in Critical Strikes for the exact scaling of these two benefits. A skill using this attribute that sees frequent use is Critical Defenses.

Dagger Mastery
Dagger Mastery increases the attack speed and critical hit chance with daggers. Also, each rank in Dagger Master adds a 2% chance that attacks from your daggers will double strike. Note this does NOT apply if you are using any other weapon. Most of an Assassin's dagger attacks use this attribute, with some exceptions being attacks under Critical Strikes and Vampiric Assault which is under Deadly Arts. One combination used very frequently is Moebius Strike together with Death Blossom.

Equipment

Weapons
Daggers come with several inherent damage types, which can be changed by the use of mods to the weapon itself. The basic damage types are Piercing, Slashing and occasionally Blunt. These damage types are then further affected by applying dagger tangs or dagger handles to the daggers.

Piercing, Slashing. Elemental daggers.
Zealous.
Vampiric.
Sundering.
The frequency of double strikes caused by a high rank in Dagger Mastery makes a Zealous or Vampiric upgrade even more effective than it would be on another weapon with the same nominal attack rate - such as a sword.

Understanding the Profession
"Glass cannons"
Assassins can be described as “glass cannons” -- they hit hard but break easily. Assassins are capable of a solo spike with lethal effect, but both their attack combos and defenses tend to be fragile. For that reason, assassins hit and run -- popping in with a shadow step or a burst of speed, then quickly escaping after their combo is completed. Some assassins are built for pressure rather than sudden solo spikes, but due to the assassin’s relatively weak armor they must be wary of attacks against their own person.

Compared to Warriors, Assassins have weaker armor, yet many of their skills function at melee range. This can place the assassin in danger, both from PvE mobs and PvP opportunists. A large consideration in the game, both in PvE and PvP, is surmounting the enemy’s defenses before your own healing is exhausted. An assassin constantly at melee range with enemies can drain a friendly healer's energy quickly.

Assassins can easily overextend past the range of their healer's ability to heal, and so must be mindful of their location relative to the healers in the party. Forcing a healer, be it a Monk or Ritualist, to extend out in an effort to heal an assassin means putting the healer in greater danger, as well as preventing the healer from doing their job of healing, as every second the healer is traveling to spell range is another second the healer isn’t healing.

Mobility
Assassins are, more so than any other class in the game, quite effective at controlling positions. This mobility is key to an assassin’s ability to quickly deal damage then escape back out while still alive. This mobility should not be overlooked for an assassin in PvE, but is especially important in PvP.

The stance Dash is the fastest speed boosting stance in the game over short distances and can be used for both offensive and defensive purposes. Dash can be used to escape an area of effect, dodge projectiles such as arrows and spells, or quickly kite out of attack range. It is also a good way to cancel out a previously applied stance with minimal recharge time.

Assassins have the unique ability to shadow step, which is a teleport that moves an assassin either to an enemy, an ally, or a prior position. Shadow steps can occasionally be useful in PvE, as seen by their use in solo farming builds or to complete certain mission objectives. However, shadow steps are much more commonly used in PvP. For example, the assassin class is occasionally taken as a secondary class on a warrior or a monk expressively for shadow stepping skills. Offensive shadow steps are often used as the opening skill in an assassin skill chain or "combo" (see assassin combos below for more information).

When using shadow steps, remember that you cannot go to enemies that you cannot normally reach by just walking there, thus if a gate is closed, you cannot go behind that gate by shadow stepping.

Attacking as energy management
Assassins, like a caster, have four pips of energy regeneration. However, assassin skills are costly and often used in quick succession as a part of combos. In order to have enough energy to complete a combo, an assassin should use some form of energy management. An assassin gains energy via attacking. This is more often a convenience rather than a hindrance as attacking is often when an assassin needs energy the most.

The inherent energy management of an assassin is the Critical Strikes attribute, which grants energy for every critical hit scored. With a rank of at least 3 in the Critical Strikes attribute, you receive 1 energy back per critical hit. At 8 ranks of the Critical Strikes attribute, you receive 2 energy back per critical hit. And finally at 13 ranks of the Critical Strikes attribute, you receive 3 energy back per critical hit.

The skill Critical Eye can increase the energy gain per critical hit. Also, any skill that increases the chance of a critical hit will indirectly increase the energy gain from attacking. For example, Wild Blow always lands critical hits, and so can be used cheaply by an assassin.

Zealous mods on weapons, which give a point of energy for each successful hit at the expense of a point of energy regeneration, are also used replenish an assassin's energy during the energy intensive combinations.

Some assassin skills give you energy directly. These skills often have "lotus" in their names. The dagger attack Critical Strike also returns energy, in addition to the normal energy gain from a guaranteed critical hit.

The skill Assassin's Promise offers an alternate means of energy management, but is only rarely used in PvP due to it’s unreliability. The assassin needs to be assured that his target will die and that the hex won’t be removed, which is far from a guarantee in PvP. Assassin's Promise can be effective in PvE, as mob deaths are more predictable and mob bars are well known. However, taking it into a PvE area where hex removing spells are common on enemy skill bars is not advisable.

Attack skill damage > Dagger damage
The majority of damage an assassin deals comes from the +damage on attack skills as the daggers themselves deal very low damage. Because daggers have the lowest maximum damage of all weapons, "Auto-attacking" (attacking an enemy without using skills) tends to be very ineffective with daggers unless their faster attack frequency is taken advantage of with "per hit" skills such as Spirit's Strength or Order of Pain.

Understanding combos
Unlike other classes, the assassin class has skills which require the use of other skills prior to activation. An assassin combo consists of running through these skills in rapid sequence. In a normal skill chain, Lead attacks are used to activate Off-hand attacks which in turn are used to active Dual attacks. A combo must be used on a single target -- you cannot start a combo with a Lead attack on one enemy and then follow up with an Off-hand attack on another.

This limitation curtails the power of the dual attacks, which would otherwise be overpowered. A Dual attack is two separate attacks, both of which receiving the damage bonuses and effects of the skill used -- combined these attack can hit for a hefty amount of damage.

The aim of a combo is to successfully hit a target with one or more dual attacks.

There are also certain skills that break the standard progression from lead attack to off-hand attack to dual attack. For example, the “black” prefixed off-hand attacks require the target be hexed. This essentially means hexing the target enemy is a lead attack for the black off-hand attacks. Another example would be Palm Strike as it is a touch attack which counts as an off-hand, and so allows an assassin to cut straight to executing a dual attack skill. Moebius Strike is an Off-hand that must follow a Dual attack, and Exhausting Assault is a Dual attack that must follow a Lead attack.

Designing a combo
Will the combo kill an enemy, or otherwise accomplish a goal?
While this is obvious, it is sometimes overlooked. For PvP, whether a combo can kill or not can be gauged by simply adding up the numbers. Also, combos that incorporate knock downs and deep wounds are popular and effective in PvP.

Some combos aren’t meant to kill with a single spike. Assassin combos can pressure, interrupt, and strip enchantments from a target as a goal. Even combos that are meant to kill with a single spike often incorporate knock-downs that can be used as an interrupt if the situation demands.

When designing a combo, the recharge times of the component skills need to be considered. A combo that can only be used once every 45 seconds isn’t terribly useful, regardless of its effect. However, a combo that can be executed often can be useful for pressuring enemies, but may lack the spiking power of a combo with a slower overall recharge.

Is there enough energy management in the build to pay for the combo?
The combos meant for solo spiking usually have high energy costs; on the order of 40 energy is typical. That would be a high price for even an elementalist to pay, and an impossible price for an assassin to pay without the use of energy management.

When designing a combo, an assassin player should look at the amount of energy he needs to spend and also ascertain how he is going to regain energy over the course of the combo. The answer is critical hits, zealous daggers, and/or the dagger attacks that return energy (such as Black Lotus Strike or Critical Strike).

How fragile is the combo? Is it easy for a target to escape?
Many assassin combos are easily thwarted, ruining the remainder of the combo. Choosing a good target at an opportune time can mitigate the fragility of an assassin combo. Beyond that, skills can be incorporated into a combo to make it less fragile.

Buffs to attack speed naturally increase the speed in which the combo is performed. This gives targets and their allies less time to react to the assassin’s combo.

Knock-downs can suspend an enemy from kiting and otherwise acting, and so are popular elements to assassin combos.

Snares, speed boosts, and shadow steps can counter kiting.

Certain assassin attacks and skills cannot be Blocked. Also, the hex Expose Defenses is a cheap way to prevent a target from Blocking an assassin's attack string.

Assassin skill names nomenclature
Many of the names of Assassin skills include keywords that be used to help guess at the effect of the attack.

Asp / Spider / Viper These skills inflict poison on the target.
Black Black skills have some extra effect on targets that have been hexed, or can only be used on targets that have been hexed.
Falling Falling off-hand attacks can only be used on knocked down targets.
Fang Causes deep wound. 1
Fox Fox skills bypass blocking.
Golden Golden dagger attacks either require the assassin be enchanted or have some extra effect on targets if the assassin is enchanted.
Lotus Lotus skills return energy.
Mantis Mantis skills cripple targets.
Ox Ox attacks knock targets down.
Wild Wild attacks remove stances.

PvE
While Assassin's are commonly used in PvP, the usage of a primary Assassin is somewhat limited. Due to their low armor and fragile dagger chains, Assassins are not commonly seen in Missions or Quests. Many people, however, prefer to have a secondary Assassin profession because of the unique skills in Deadly Arts and Shadow Arts. Assassins also have a rather bad reputation among PvE play because when Guild Wars: Factions was first released, players new and inexperienced to the Assassin class started using them as "tanks", which was a poor choice which resulted in frustration from many players. However, Assassins are also the best running class in the game, and are usually primary or secondary Assassins.

Fast-Killing with Assassin's Promise
Many assassins use complete parties of henchmen, as these are easy to focus on one target. Then they hex the called target with Assassin's Promise and then quickly kill that target to get back energy. This allows for using combos with higher cost.

Farming with an Assassin
Farming as an assassin is usually done as A/E using Shadow Form to be invincible. The general strategy is shadow stepping in an enemy mob, killing that mob with many PBAoE(Point blank area of effect) spells and then shadow stepping back in case some monsters survived. Frequently seen skills are:

Shadow Form
Arcane Echo to maintain Shadow Form
Shadow Walk or Shadow of Haste together with another stance for shadow stepping
Dash or Dark Escape as a cancel stance
See PBAoE for offensive spells

Hard Mode considerations

As assassins are generally easy to defeat, it is important to be less fragile in hard mode. This problem can be solved either by adding defensive skills or staying out of melee range.

PvP
In GvG
Most Sin builds in GvG involve splitting with Shadow Prison Bars, or Aura of Displacement Bars. New metas are appearing however where Assassins are used for the elite skill Shattering Assault instead of warriors.

In RA(Random Arenas) and TA(Team Arenas)
Assassins lack healing abilities and have low armor. That's why they depend strongly on a monk in arenas. The currently most frequently used builds are ones combining Moebius Strike with different dual strikes.

Very often used build parts are these combinations:
Black Mantus Thrust
Jungle Strike
Trampling Ox
Falling Lotus Strike
Blades of Steel
Dancing Daggers
Entangling Asp
Signet of Toxic Shock

Other frequently used skills include:

Augury of Death
Critical Defenses
Shattering Assault
Shroud of Silence
Siphon Speed
Deadly Paradox, often combined with
Feigned Neutrality

In HA
In Heroes' Ascent, assassins played a role as targets for Ancestors' Rage in a ritualist spike team. This is no longer possible, though, because now, Ancestors' Rage does not stack with itself if more than one person uses it on the same target.

They are also still used in the popular "Sinway" build, which utilized two lead Assassin spikers to quickly dispatch enemy healers and casters.

In Alliance Battles
Assassin's are a rather good profession to use in Alliance Battles. Their unique Speed Boosting skills and Shadow Steps are useful in the large-scale Alliance Battle maps, but when targeted by enemy mobs, they are easily killed.

When taking an Assassin in battle, consider the following skill combinations:

Aura of Displacement is extremely useful for ganking purposes. You can easily dispatch a lone player utilizing Golden Phoenix Strike as your skill for starting off a chain, quickly followed by a series of devastating dual attacks such as Horns of the Ox.
Shadow Walk can be used as a non-elite, non-enchantment alternative to AoD. This way, you can still utilize effective dagger chains that use elites such as Moebius Strike + Death Blossom, and use a cancel stance like Dash or Dark Escape to return to your original location.
Dark Escape is a good speed boost and can be used to kite from enemies as well as quickly capture shrines. This skill is commonly used in favor of the non-attribute skill, dash, as Dark Escape also halves the damage you take.

Staying alive

Defenses and self-heals
Assassins have a variety of defensive and healing skills at their disposal. Most of these are found under the attribute Shadow Arts

Defense through damage reduction
Blocking is a widely used method of reducing damage. For the assassin blocks can come from enchantments like Critical Defenses or stances like the elite Flashing Blades

The main source of damage reduction for the assassin is mobility. A variety of skills can be used to avoid the sources of damage. For example by causing the crippled condition on melee attackers and then kiteing them, so they cannot land a hit. Speed boosts like Dash can also be used in that manner to avoid harm. Finally the assassin can use shadow stepping skills like Death's Retreat and Return to fall back into his allies ranks. Most of these mobility skills can be used in both offensive and defensive ways.

Healing
When avoiding the damage was not enough, healing is needed. The two main healing skills of the Assassin are Shadow Refuge and Feigned Neutrality. Each of them provides a significant amount of health regeneration. Shadow Refuge functions as a combat healing, since it also adds additional healing when it's user is attacking while it ends. On the contrary Feigned Neutrality is removed once the Assassin attacks or uses a skill. However, it adds an armor bonus of 80 while it lasts, making it a good skill to use for a charge and retreat tactic. For sustained healing while in combat, Way of Perfection can be used. Especially when a high number of critical hits are certain.

Playing in a Party
One must remember that an assassin is NOT a warrior. Going into battle before your other teammates is never a good idea.

In PvE, allow the warrior or dervish to cause and maintain aggro. That way, the enemy AI will focus on someone other than you, allowing you to unleash your attacks on any pivotal or inconvenient opponents.

In PvP, assassins must be speculative with which targets to attack. It is also best to stay in the back until the time is right, rather than to stay in battle and, more than likely, be killed.

An assassin is a unique support profession, in which damage is the main, and only concern when contributing to a party. Remarkable mobility and survivability should not be overlooked, and courtesy to the healers of the group will be rewarded.

As for every other profession, an assassin must pay attention to the status of the group, and go with the ebb and flow of battle.

What to Avoid
As assassins are weak in terms of armor, they can easily overextend and die.

Play Styles

Critical Barrager
The elite bow attack Barrage removes ranger preparations, as a limit to the damage it can deal. However, Barrage can benefit from an assassin's attack buffs, including Critical Eye and the Critical Agility, Sharpen Daggers and Way of the Master enchantments. This build is sometimes known as a "bloody barrager" from using Sharpen Daggers to spread bleeding on large packs, something non-trivial for rangers.

In order to be effective, a barrager needs numerous targets packed in tight together. This situation rarely arises in PvP, but is frequent in PvE.

The non-elite Volley can be used in the same way, freeing up the elite slot.

Due to the better chance of a critical hit, some other bow attacks can benefit from an assassin's Critical Strikes attribute, including Disrupting Accuracy and Keen Arrow.

Non-melee Assassins
A few common assassin builds are based on Deadly and/or Shadow Arts, with little or no melee attacks.

Death Spike Death Spike uses the skills Entangling Asp and Iron Palm who recharges are reduced by Deadly Paradox to cause a 4 second lockdown that quickly renews while fueling the poison requirement of Signet of Toxic Shock. At max DA this combo can easily hit for 150 damage. Combined with Dancing Daggers and Augury of Death this is a potent combo but, it is also extremely draining as you will not be able to use Critical Strikes to refuel. Due to repeaded nerfing of Deadly Paradox this combo has been greatly weakened.

Shadow Form plus Sliver Armor

Snares and Debuffs

Choice of Secondary Professions
Monk, Ritualist or Paragon is often used to provide a resuable Resurrection skill.

Ranger: In PvE, a bow can be used for a critical barrager build.
Dervish: Dervishes have a number of defensive skills. Additionally, Way of the Master works particularly well with a scythe in PvE.

Click here to view a list of Assasin skills.