General principle

The name 55 monk stems from the hit points of the character. Due to the fact that Protective Spirit caps damage taken at a percentage of current max health rather than a base value, a character using the skill with very few hit points can reduce individual sources of damage down to very low amounts, which can then be easily healed with health regeneration skills. 55 health is the minimum amount of health obtainable with currently in-game items (not counting death)

Basic knowledge

To use this type of build, the character must be either a monk primary or secondary (level 20). Primary is more widely used to gain maximum benefit from the superior runes used, many skills available to a monk fit very well into this bar, and the monk's inherent divine healing bonus increases survivability. To reach the 55HP, the character will use 5 Superior Runes, each one giving -75HP, even if the fifth one will be useless (with the exception of Elementalists and Warriors, all professions have only 4 attributes and since runes do not stack, the 5th won't provide any advantage except to lower max health). It will also use a Grim Cesta obtained from the Cities of Ascalon quest that has a -50hp Mod. This will bring the character to 55hp.

The character will then use the spell Protective Spirit to reduce damage. Having 55hp, they will only take 5 damage per hit or spell, which can either be countered with health regen or with the healing bonus of divine favor, or alternatively by further reducing the damage through the use of spells such as Shield of Absorption, Shielding Hands or Stoneflesh Aura. For health regeneration the character uses skills like Mending, Healing Breeze or Watchful Spirit.

To ensure a constant flow of energy, 55 monks will use Balthazar's Spirit with the very high number of hits they will take it will grant them a constant inflow of energy during combat, the time energy is most required. It is also possible to use Essence Bond which will cause energy gain only on physical or elemental damage. Both can be used if the user wants a very high energy gain. It is highly advised to use Radiant Insignia to have a high base energy. A +5 energy inscription on the main hand weapon is also desirable, but not essential.

The killing will usually be done with skills that damage the foes when attacking. The most commonly used is Shield of Judgment, but some others are widely used such as Sliver Armor and Spiteful Spirit.

Side skills

The 55 monk is a very flexible build, the core of the build is Protective Spirit, a life regeneration skill, an energy management skill and a way to deal damage. Many variants exists depending on the area the build will be used.

Spell Breaker is commonly used to avoid harmful hexes, enchantment shattering and life stealing spells which bypass Protective Spirit.

To kill healing bosses and in areas where monsters use adrenal skills to interrupt, Sympathetic Visage (or the copy skill Ancestor's Visage) can be used as they will lead the foes to quickly have no energy or adrenaline. They can be used along with Mind Wrack in duo with Famine. It should be noted these spells will only work against melee attacks, so to energy drain ranged spell casters the character should position themselves adjacent to the caster so melee attackers will energy drain both themselves and the caster.

-Balanced Stance is another skill to consider when foes can knockdown.
-Blessed Aura is very widely used as it extends the duration of Protective Spirit and other monk Enchantments.
-Spoil Victor is a very good boss killer as it deals heavy damage, and you will often meet the condition with 55 life.
-Blessed Signet is a good way of providing yourself energy if you use (and you should) maintained enchantments like Blessed Aura, Mending or Retribution.

Battle behavior

55 monk is designed to farm in PvE, it is too fragile for PvP or normal PvE play, and wouldn't have any use as a simple enchant removal, life steal or heavy degeneration would kill you almost instantly.

Death

If they die, a 55 monk will end up with 1 hp when they are resurrected and will be very vulnerable. Most of the time, people just remove the cesta so they end up with 33hp. Sometimes they use a -20 hp focus allowing them to suffer only 1 damage per hit. Note, any spell which resurrects a character with a percentage less than 51% of their health will not work on the character. Skills that resurrect at 100% health (such as Resurrection Signet) or at a fixed amount (such as Flesh of my Flesh/Resurrection Chant) would be required.

Life degeneration

Foes often apply life degeneration, commonly with conditions such as Bleeding or Poison. In these situations, life regeneration skills are very important and should be maintained vigilantly. Healing Breeze is an effective tool in this sense, with high regeneration, decent length, and with proper energy management, easy enough to maintain. Mystic Regeneration is another popular regeneration skill on 55 monks because of the number of enchantments they place on themselves.

Disadvantages

These builds, while sometimes called invincimonks, are in fact fragile. Some skills, especially life stealing, ignore Protective Spirit and will kill the monk in one hit. Enchantment removal is also hard to cope with -- with practice, single enchantment removal spells can be countered using cover enchantments, but for countering mass enchantment removal Spell Breaker would be required in place of a damaging elite skill such Shield of Judgment or Spiteful Spirit as detailed in the basis of this build. Non-targeted enchantment removal such as Well of the Profane or Disenchantment or non-spell enchantment removal such as Expunge Enchantments cannot be countered. This build is not suitable for use with heroes as the hero AI lacks the ability to correctly maintain the necessary enchantments. However, if you shift-click disable the enchantment spell, then make the NPC Hero cast it on you it will be maintained as long as it remains disabled via shift-click.

Skills

A common set of skills used in this build are: Essence Bond, Balthazar's Spirit, Mending, Shield of Judgement, Healing Breeze, Protective Spirit (essential) and Blessed Signet (energy gain after enchantments have been cast). Skill sets may vary from each secondary profession. Mesmer skills like Arcane Echo, for example, can be used in place of Retribution to double up on Shield of Judgement, because of the long recharge time associated with it.


Information from wiki.guildwars.com