Guide to defeating doppelganger

The following tactics have been suggested to beat the Doppelganger:

General Tips:

 * The Doppelganger will have the same skills you equip, so don't equip any skill you wouldn't want used against you.
 * Think very carefully before bringing any skill that can be used to heal yourself.
 * Equip lots of slow-casting self-buffs: the less useful in the one-on-one fight, the better. The AI will waste time at the beginning of the fight casting every buff on itself.
 * For all ranged attackers, stay on higher ground. Ranged attacks from higher to lower ground do more damage.
 * Cast any self-buff enchantments before stepping on the third stone that starts the cutscene. They will last into the match. Cutscenes no longer run in real time, so any "duration" enchantments will not expire or run down their time during the cutscene.
 * Dodging arrows: Stand as far away from the doppelganger as you can be and still cast spells on it, and tap Q and E (Or strafe left and right, if you have them rebound) as fast as you can. Tap them both, many people hear that and try to only tap one. This twitchy movement will cause the AI to shoot wide and miss most of his shots (You can do it slower, but doing it really fast takes less practice)

Elementalist Tips:

 * Bring lots of skills with very long cast times, and only one or two spammable skills. The Doppelganger will usually focus on the slow-casting skills and allow you to gain the advantage by wise use of the spammable skills. This is not foolproof, but the AI tends to use all of its skills relatively evenly, whereas a human is smart enough to focus on different skills at different times. For example, Fireball and Fire Storm are good choices if you take Meteor Shower - hammer at it while it casts Meteor Shower, then dodge out of the way when the skill completes. By the time it has finished you will have a huge health advantage.
 * Do not equip skills that could disrupt your spell casting (like Gale or Earthquake).
 * Bring Air Attunement, Earth Attunement, Fire Attunement, Water Attunement, Flare, Fire Storm and Meteor Shower, with all the points in Energy Storage and Fire Magic. While the Doppelganger casts the attunements, cast Fire Storm and Meteor Shower, then spam it with Flare.
 * Bring Iron Mist, and no lightning damage.
 * Mark of Rodgort and a fire wand/staff - the Doppelganger doesn't have a fire weapon so you will have the advantage.
 * An E/Me could take their chosen element and Physical Resistance, with 0 Inspiration Magic, and leave the doppelganger to use it (similar to taking Frenzy on W/X and X/W). The extra damage caused should give you an advange over your doppleganger.
 * An E/Me bringing Blinding Flash and Empathy, causing Doppelganger to miss with his attacks while dealing damage to himself at the same time

Mesmer Tips:

 * An IW Mesmer would have no trouble defeating doppelganger. If you skip the cinematics, you can easily cast spells such as Illusionary Weaponary, Illusion of Weakness, or other enchantment before-hand, killing him very quickly. Using a +3 Illusions rune in addition to your mask would mean that you have four extra levels in all those skills, and should guarantee success. Equiping Illusion of Weakness would also make the doppelganger cast it at the beginning, giving you lots of spare time to attack; it is easily possible to kill him within 10 seconds. Another possibility without Illusionary Weapons is to use Illusion of Weakness in combination with multiple degeneration skills. Degen does not trigger Illusion of Weakness, and this makes killing him very quick.
 * Bring Backfire and Empathy and maybe some spammable skills (like Flare, Wastrel's Worry or something with a really fast cast and recharge time). Put all points in domination.  The AI is not smart enough to refrain from casting or attacking while hexed with those skills and will quickly kill itself. Once they are cast, do nothing.  The Doppelganger will kill himself shortly.
 * Power Spike and Diversion are very useful if coupled with a few Elementalist skills with long casting times. The Doppelganger will tend to use slow-casting skills early, so these two skills can be used effectively. Be careful not to use the Elementalist skills yourself, because the computer AI is deadly in detecting such spells and interrupting them.
 * Illusion of Haste is often a good idea. The Doppelganger will waste time casting it (and give itself an enchantment you can use Shatter Enchantment on), but since neither of you is likely to be chasing the other, it will do little good.
 * Don't bring a lot of interrupts. The AI almost always has faster reflexes than you, so you'll get interrupted more than it will. Only bring interrupts if you have also equipped a skill with a very lengthy cast time (let the AI use this skill, ignore it yourself).
 * Be careful if you bring any skills that damage the opponent's energy, such as Energy Burn or Energy Tap. Although the exact amount of energy that the Doppelganger has is unknown, it's almost certain to have more than you.
 * Ether Lord can be extremely effective or completely worthless, depending upon luck. If the Doppelganger casts it early on, it will have a distinct energy disadvantage. You may wish to combine it with Mind Wrack in hope of the AI draining its own energy with Ether Lord, thereby triggering Mind Wrack.
 * Allocate all your attribute points in Domination Magic and put the remaining points in Illusion Magic and equip Distortion and Empathy. Keep the doppelganger constantly hexed with Empathy while always keeping yourself under Distortion and it should attack until it dies. Also, try to keep in its melee range so it will have a higher attack rate.
 * On the same note, if you have access to Signet of Midnight {which is highly unlikely}, bring that instead of Distortion. Also bring skills that will allow him to further increase his attack speed (such as Frenzy and Tiger's Fury).
 * The AI generally uses skills left to right so put lots of useless spells on left and backfire on right. If you cast backfire in the first few seconds the doppelganger usually dies in about 6 seconds.
 * A very quick and easy way to kill the doppelganger would be to make full use of "Boottspurr's Combo": Put 4 attribute levels into Illusion, 12 levels into Domination, and the rest in Inspiration (plus whatever runes you have for each).  Equip Distortion, Spirit of Failure, Empathy and Backfire;  Cast Spirit of Failure on the doppelganger as soon as the fight starts, followed by Backfire then Empathy, once that is done, simply spam Distortion.  This will have the doppelganager missing 81.25% of his attacks, and you gaining energy each time he does.  He will quickly kill himself by attacking or casting spells to no effect.
 * A Me/E could bring the 4 attunement and Backfire. Cast Backfire at the beginning of the fight and watch your doppelganger die :-).

Monk Tips:

 * Consider bringing Healing Breeze. The AI currently will not use Healing Breeze for ordinary healing. However, it does use Healing Breeze to counter health degeneration from conditions or hexes.
 * Consider Retribution. The AI does not cast this enchantment on itself, and is a good way to deal extra damage without any casting costs.
 * Bring Smiting Prayers. You can reportedly cast them faster than the AI will. You can defeat the Doppelganger by only using Zealot's Fire and Reversal of Fortune.
 * Bring useless maintained enchantments. If you bring at least four, then the AI will cast them all on itself and have no energy regeneration (or even degeneration if you have more than four). Divine Boon will cost them extra energy when they heal; when they run out of energy they will stop healing and have no benefit. Life Attunement will make them deal less damage; since they cannot heal due to lack of energy they get no benefit. Blessed Aura is good too, since they cannot cast enchantments due to the afore mentioned lack of energy. Holy Veil is good if you don't plan to use hexes.
 * If you are a Necromancer/Monk or Monk/Necromancer, bring Scourge Sacrifice, Awaken the Blood and Order of the Vampire. No other skills are needed, merely cast Scourge Sacrifice on the Doppelganger, and wait for it to kill itself. Low-levels can try bringing Defile Flesh, Dark Pact and Awaken the Blood and not using them, which has a similar effect, making sure Healing Breeze and Reversal of Fortune (and Pacifism to give time for health regeneration) are there to keep yourself alive.
 * If you are using a Necromancer/Monk or Monk/Necromancer that has been to Cantha, bring Scourge Sacrifice, Awaken the Blood, Cultist's Fervor and Order of Pain. Simply use Scourge Sacrifice and watch your Doppelganger sacrifice more than 100% health (it will use Sourge Sacrifice, followed Awaken the Blood and Cultist's Fervor before using Order of Pain)
 * If you are a Monk/Necromancer or Necromancer/Monk, bring useless enchantments, such as the ones mentioned above, and Rend Enchantments. Cast the enchantments on yourself and the doppleganger will lose over 200 health when he does cast this spell. Also, bring other skills that require him to sacrifice health, such as Defile Flesh, Dark Pact, etc.
 * Just Healing Breeze (with 9 or more ranks in Healing Prayers), Smite and Banish can be used to defeat doppelganger with no trouble within about 45 sec.
 * An alternative is to bring only a staff (or any other weapon) and Healing Breeze. Keep Healing Breeze up and defeat the Doppelganger with your staff. Depending on staff stats this is extremely fast.
 * Use Pacifism on the doppelganger when you are low on health, then cast Healing Breeze. You will be able to safely regenerate a large amount of health before Pacifism expires.
 * Another way (fairly expensive) is to use a Mo/any Invincible Monk build to tank the Doppelganger and slowly kill him with a weapon or careful usage of Zealot's Fire.
 * Protective Bond is another option, as Monk Primaries will often not have the punch to deal over 5% damage to the Doppelganger, while it has no trouble triggering the Protective Bond effect. No other skills are needed.
 * Max your Smiting Prayers, but spend 0 points to Healing. Bring Scourge Healing and Orison of Healing. Fill the rest 6 slots with smiting skills. Hex the Doppelganger with Scourge Healing, do some damage on him/her, and he/she will kill him/herself with Orison! You can also do this with Heal Area so the doppelganger will heal you aswell and take double damage from it. Warning: don't use Orison while you are hexed with Scourge Healing! Don't bring hex removing skills!

Necromancer Tips:

 * Bring spells that require a health sacrifice. Don't use these skills yourself, but rather let the doppleganger use them. By including Awaken the Blood and/or Cultist's Fervor as the first skills in your skill bar, the doppleganger will use them first, thereby increasing the health sacrifice. An N/Mo may wish to bring Scourge Sacrifice in order to further increase the health sacrifice.
 * On top of skills that sacrifice health, skills that inflict conditions upon yourself are great opportunities. You are smart enough to stay away from Signet of Agony and Chilblains (not to say that those skills are not useful, merely that they do not help in this particular situation), but the AI is not, thereby cursing itself with Poison and Bleeding while you only take a small amount of damage. If you have access to Virulence, use it with these skills to further the degen (as long as you don't have any other skill to allow it to cause or transfer a condition to you).
 * Keep Enfeeble and Insidious Parasite on the doppleganger and let it attack you in melee. If you have it, add Spitefule Spirit to further its demise.
 * Cast Price of Failure and keeping a distance, dodging arrows to cause it to trigger. Again, Spiteful Spirit will help expediate its death.
 * If using one of the many strategies which involve you doing very little casting, bring Malaise to cause it to give itself health degeneration.
 * If you are a Necromancer/Monk or Monk/Necromancer, bring multiple monk enchantments that are useless for the battle along with Rend Enchantments. Cast the enchantments before entering the battle and let the doppleganger rend them thus damaging itself.
 * Don't bother with vampiric skills or hexes such as Life Siphon or Life Transfer. The AI will likely also cast them on you, so at best it will be an even trade and cancel out.
 * Remember that there will be nothing dying in this battle, so not only will Soul Reaping be worthless, anything that requires a corpse (such as any Wells, any Minions, Soul Feast, Consume Corpse, Necrotic Traversal, etc.) will do you no good.

Ranger Tips:

 * Bring many slow-casting Nature Rituals like Winter and Quickening Zephyr (the less useful in the one-on-one fight, the better). The AI will waste time casting the rituals while you apply the attack.
 * Three main skills to equip would have to be, Throw Dirt so you can blind them and get a few more points, Troll Unguent if you're a person with a tendency to lose health quickly, and Distracting Shot so if you have the Unguent equipped, then its best to use Distracting Shot while he/she's trying to heal him/herself
 * Longbows and slow-firing bows such as Hornbows are generally a bad idea. Bring the quickest firing bow that you own (Shortbow or Half Moon) so you can get off as many shots as possible while your double is casting Nature Rituals or traps. By the time they get around to attacking you, they're nearly dead already.
 * Equip a lot of effective bow attacks, once the battle begins, charge right in next to it and attack, because it will disable him/her using bow attacks, since they will equip their axe.
 * Bring evasion skills like Dodge and Lightning Reflexes, Throw Dirt, and traps. You will avoid your doppelganger's attacks, but can lead him onto your traps because he will chase you to throw dirt.  In this way you can beat your doppelganger without ever firing an arrow.
 * Bring 7 slow-casting Nature Rituals and the elite, Poison Arrow. As long as you are up close, right next to him, he won't use poison arrow, because he's using his axe. He will cast all 7 Nature Rituals. This is possible at very low levels, and works to get the bonus.
 * A good way for a Ranger/Monk to defeat the Doppelganger is to bring at least 5 spirits, Balthazar's Aura, and Symbol of Wrath with a maxxed Smiting Prayers. Before you step on the third circle, cast Balthazar's Aura. Then, step on the circle, skip the cut scene, get close to the Doppelganger, and cast Symbol of Wrath. Then, while he is casting spirits (he may cast Symbol of Wrath before that), attack him with the spells and a bow.
 * Hunter's Shot, with the Canthan elite skill Heal as One plus a few of your favorite pet skills, and a few useless nature rituals will dispatch the doppleganger very effectively, without risk. Get close, and let your pet do the work.  Use Heal as One if you get into a bad situation, as it relies upon beast mastery, and is useless to the doppleganger.  Max out your survival and beast mastery, and dump everything else into marksmanship.  This battle should last about 15 seconds.

Warrior Tips:

 * Equip Frenzy but don't use it. The AI will use it, putting itself at a significant disadvantage in the one-on-one fight. Couple this with a few energy based attacks which you can use right away (ie Power Attack, Seeking Blade/Irresistible Blow/Swift Chop, Griffon's Sweep, etc.) and the Doppelganger should be down in 15 seconds or less.
 * Bringing Hammer Mastery or Swordsmanship skills exclusively does not work. Despite wielding an axe, the Doppelganger will still be able to use these skills.
 * Activate skills in the most effective order for a fast take-down. Sever Artery works best before Gash but your opponent doesn't use it that way.  Similarly, do not use Final Thrust until your opponent is below 50% health; your Doppelganger doesn't understand that, and will waste a lot of adrenaline by using it prematurely.
 * Any skills with a "Lose All Adrenaline" component, such as Wild Blow, can be a great benefit. Ignore them yourself, but let the AI waste its own adrenaline using them on you.
 * If your secondary class has high-energy spells, bring some of those that don't really do anything useful. For instance, if you are a Warrior/Mesmer, bring Imagined Burden.  It uses 15 energy, and slows 50%.  That won't matter since you aren't running anywhere, but it will use 15 energy from the Doppelganger.  This may be appropriate for other classes as well, but has only been (very successfully) tested on Warriors.
 * Because the Doppelganger uses a Chaos Axe, a tactics Warrior should consider Riposte and/or Deadly Riposte. Both skills can deal large amounts of damage to the Doppelganger, but won't be used against the player.
 * An easy win for W/Mo in under 10 seconds is to bring Life Attunement and Frenzy with 12+ hammer mastery.
 * By far the easiest way for a Warrior primary to Ascend is to unequip all skills, and merely take a maximum damage sword (15-22 damage). Get in close, and hack away. As long as you actually have a full set of high level armor (either the armor from the various collectors, or a complete set from Droknar's Forge), Ascension in this matter should be approximately 35-40 seconds, depending on the amount of critical hits
 * Bringing Healing Signet could be useful if you have a fast attack rate or high-damage hits. Once the Doppelganger is hurt, it will cast it upon itself. But, with the &minus;40 amour that the signet delivers during the duration of the spell, you can deliver more damage than it can heal; the Doppelganger will continue attempting to heal itself until it dies. This is a good time to finally use Frenzy.
 * For a W/Me, bring Elemental Resistance (or Physical Resistance if you're using a weapon with an elemental pommel, e.g. with ebon, icy, fiery, or shocking, before the name of the weapon) with 0 points in inspiration, but dont use it, let him use it, this'll give you the upper hand with him taking extra damage from the opposite type.

Ritualist Tips:

 * Equip Soothing, Shelter, Shadowsong, Pain, Bloodsong and Dissonance and bring your Communing attribute as high as possible. As soon as the fight begins start summoning spirits, starting with Dissonance (to keep him from summoning a spirit army himself) and going backwards in the list. You don't need Soothing and Shelter, they are only equipped to keep the Doppelganger busy and reduce the chance, that he also starts with Dissonance. Typically he will be dead within 25 seconds.
 * Equip only Vengeful Weapon, and have max restoration magic. Repeatedly spam on yourself for an easy win.

Assassin Tips:

 * Bring a pair of vampiric daggers and no skill at all, max critical strikes and dagger mastery, you're done.
 * With all points in daggers and critical strikes, you can outdamage the doppleganger if you have the +15 while attacking armor.
 * Don't take any dual attacks, but include hexes that trigger on them to have the doppleganger waste its time and energy casting them.
 * As a general rule, if you can start a dagger chain that you can use but the doppleganger will not, it is quite easy to outdamage it. Falling Spider and Horns of the Ox make a great combination that can be alternated to keep an ongoing chain of damage and degen on the doppleganger. By utilizing methods to knock down the doppleganger (allowing Falling Spider) that it will be unable or unlikely to use, you can start the chain without worry of retaliation.  An example of this is to be an A/R and bring a pet. All you need is pet attack to cause a condition, follow with Iron Palm, and now you have the knock down to start the chain.
 * Bring Viper's Defense, Heart of Shadow, and Seeping Wound. Never attack. Use Viper's Defense to poison it and Seeping Wound to add to the degen. Dodge arrows while it is poisoned to reduce damage. Use Heart of Shadow to regain health. This method is slow, so you may not get the bonus, but it will give you an easy win.