Raid

from soluuloi (official Forum), edited by terojen, edited by Galen

Rarity
The higher your rarity, the more likely you will be attacked by high level players. All proof ingredients have a rarity value so they are usually the most common item stolen from raids. You can protect your rare equipment by always having them equipped on a character.

Notoriety
Notoriety is how infamous you are. The more you raid, the higher it goes. The raid list is sorted by notoriety, so if you raid other players a lot you will be targeted more by high level players. You can decrease your notoriety by paying gold, but it is expensive. You also gain more notoriety the higher your opponents notoriety, but conversely, if you attack someone with low notoriety you gain less gold than normal.

Civilization
Civilization is your building point. The more you build, the higher it is. Usually, strong players have high civilization point. Raider tends to ignore them.

Guild
Join a guild is a must to survive. Without guild, you will have 3 defenders at most (1 defender per fort). It will be very easy for the raider to finish your defenders in 5 turns. With guild, when you are being attacked, guild garrison will send 1 or 2 more characters to help you. Sure, even if the raider is stronger, he may not able to finish 5 characters in 5 turns. With guild, when you raid someone, guild garrison also send 1 character to help you. It will make your raiding easier. Note that the lvl of the characters that you use to raid or to defend a raid must be close to the lvl of the guild garrisoners for them to help you. For example: your defenders are all lvl17 and all of the guild garrisoners are from lvl30 to lvl40, they will not help you. If I remember right, the different in lvl must be lower than +/- 5.

How to defend yourself
Check this post on some information on raiding. - The Art of Defence