Damage calculation

Damage Types
There are several different types of damage in Guild Wars. There is also Health Degeneration, which, while not considered damage by the game engine, will nonetheless hurt a player or monster.
 * Elemental damage
 * Fire damage
 * Cold damage
 * Lightning damage
 * Earth damage
 * Physical damage
 * Blunt damage
 * Piercing damage
 * Slashing damage
 * Special damage:
 * Holy damage and Light damage
 * Chaos damage
 * Shadow damage and Dark damage

Damage Calculation

 * Does its damage type get changed?
 * Does it hit or get Evaded?
 * Does its get modified in amount? (depending on its type and level)?
 * does it ignore Armor?
 * Calculate resulting Damage with Armor and armor penetration:

[Source]
 * Base Damage is just a simple factor, two weak attacks always equal one attack that is twice as strong.
 * Weaker Armor (depending on damage type) is slightly exponentially worse than stronger armor.
 * Higher armor penetration makes this slightly more exponential.

Damage Groups
There are also two damage groups in Guild Wars
 * Spike Damage
 * Damage-Over-Time