The various FRACTALS are referred to by the developers as ISLANDS (a.k.a. zones, instances, or mini-dungeons). All islands have VERY SPECIFIC mechanics which MUST be followed in order to progress. You can learn about the mechanics for each island at this link.
Walking into the Fractal gate will take you to the staging island. This island is safe and has merchants. Feel free to go through the fractal gate and look at what the merchants have to offer in exchange for Fractal Relics and Pristine Fractal Relics.
The difficulty scale of a Fractal starts at level 1 and can be increased up to level 100. Increasing the difficulty scale will make enemies hit harder, have higher toughness, have more health, and even give them new attacks. Getting into the higher difficulty scales will make some enemies so powerful that they will one-shot you, no matter how defensive your attributes are.
Agony is a unique effect similar to Poison condition.
Agony only starts being applied at difficulty scale 20.
Agony will remove a flat percent of your max health every tick. Increasing difficulty scale will increase the percentage. (approximations)
Difficulty 20+ tier = 10% health loss per tick
Difficulty 30+ tier = 31% health loss per tick
Difficulty 40+ tier = 53% health loss per tick
Difficulty 50+ tier = 74% health loss per tick
Difficulty 60+ tier = 95% health loss per tick
Agony reduces ALL healing you receive by a fixed 50% (Poison by 33%), including reviving heals received when downed. Fun fact: the massive revive heal given by certain skills (like Warrior's elite banner skill) can be reduced by Agony (and Poison) to the point where the downed ally is not revived.
Agony CANNOT be removed, but will expire.
Agony is occasionally applied to everyone in an area and CANNOT be avoided.
Certain enemy attacks will inflict Agony which CAN be avoided with a well timed dodge, block, or reflect.
http://wiki.guildwars2.com/wiki/Agony
“Madness! How can I defend against this?!?”
You can add Agony Resistance (AR) to your Ascended equipment (weapons, armor, trinkets, back item). AR can reduce damage dealt to you down to 1% health loss per tick, but no lower. Here is the amount needed to get down to the 1% minimum. (approximations)
Difficulty 20+ tier = 25 AR
Difficulty 30+ tier = 40 AR
Difficulty 40+ tier = 55 AR
Difficulty 50+ tier = 70 AR
Difficulty 60+ tier = 85 AR
Difficulty 70+ tier = 100 AR
Difficulty 80+ tier = 115 AR
Difficulty 90+ tier = 130 AR
Difficulty 100 tier = 145 AR
Buy Versatile Simple Infusion from a merchant in the Fractal staging island using Fractal Relics currency. Combine (+1) Agony Infusions with an Artificer to put into (Infused or Attuned) rings or back items.
https://wiki.guildwars2.com/wiki/Agony_Resistance
Your account has a Personal Rewards Level (PRL) which starts at level 1, just like the Difficulty Scale. When you complete a Fractal (set of 4 islands) Difficulty Scale which is AT or ABOVE your PRL, your PRL will then increase by 1. I will give examples.
Your PRL is 10. You complete a Fractal Difficulty Scale 2. You receive PRL 2 rewards. Your PRL does not increase.
Your PRL is 10. You complete a Fractal Difficulty Scale 10. You receive PRL 10 rewards. Your PRL increases to 11.
Your PRL is 10. You complete a Fractal Difficulty Scale 33. You receive PRL 10 rewards. Your PRL increases to 11.
Every island will reward you with a chest. In each chest will be Fractal Relics, (+1) Agony Infusions, and other items.
Starting at Difficulty Scale 31, wild card effects are introduced into Fractals known as Mistlock Instabilities (MI). The effects of MI are on a pre-defined list at the link below. MI will make you rethink your weapons, utilities, traits, positioning, play style... everything... Here are a couple of examples.
MI for Difficulty Scale 51 will cause enemies to explode when you kill them, dealing severe damage to you AND knocking you back (avoid standing near cliffs, lava pools, traps, et cetera)!
MI for Scale 31 strips all your boons when you dodge.
http://wiki.guildwars2.com/wiki/Fractals_of_the_Mists#Mistlock_Instability
Be Warned! Difficulty Scale is NOT downscaled, no matter what your PRL is.
Be Warned! AR on weapons and armor is only active if the equipment is active. Some examples.
Your staff has AR, but your hammer does not. AR will be lower when using the hammer.
Your head armor has AR, but your breathing apparatus does not. AR will be lower when under water.
Your terrestrial weapons have AR, but your aquatic weapons do not. AR will be lower when under water.
Your armor piece has AR, but is broken. AR will be lower until it is repaired.
Be Warned! There are NO repair vendors once the Fractal has started. If you are defeated so much that your armor is broken, you have three options. Reminder: Your first 7 defeats will DAMAGE your 6 armor pieces and back item. Any subsequent defeats will BREAK your armor and back item, nullifying them.
Use an Instant Repair Canister.
Log out to the character screen. Log back into your character and you will be in Lion’s Arch with a “join your party in Fractals” prompt. Do not close this window. Find and use a repair vendor. Accept the “join your party in Fractals” prompt.