Missioning is a system introduced as part of the Conquest Expansion. Missions are a series of repeatable instance quests that you can do to earn Loyalty Points (LP). Missions are issued by a series of NPCs and which mission you get is randomly selected from a pool of available missions. There is no cool down and you can immediately do another mission.
Missions are unlike other instances in that the party size is not hard-fixed. A single mission will have 4 difficulty levels and each level has a recommended size which is listed. This size can be ignored, though it does affect rewards (see below). When a mission is completed all party members will receive a reward in the form of loyalty points. Which difficulty level you receive depends on which mission giver you speak with.
Missions are located in cities within the conquest continent. Each city has its own mission givers, loyalty points, and reputation points which are bound to that city. You cannot spend LP from one city in another city.
Mission rewards are in the form of loyalty points. How much LP you will get for a particular mission is noted before you accept it. Everyone in the party will receive that amount of LP. So if a mission says it will give you 100 LP then you and everyone in your party will get 100 LP each. However, if you bring more people than the recommended party size for that mission the reward will be recalculated as (reward * recommended party members / actual party members) LP each. So, if the recommended size is 2 with a reward of 100 LP and you bring 1 or 2 people, everyone gets 100 LP each. But if you brought 4 people then everyone would get 50 LP instead.
Mission levels, except for level 1, require reputation points (RP). At the start of your missioning career, you will only have access to level 1 missions. To gain access to higher level missions you must either run level 1 missions or run higher level missions with someone that has access to them. Your RP only decreases if you fail missions and only the party leader loses RP for failing a mission. Other people in the party only gain 1/10th the RP that the leader gains. This is rounded down. The max RP you can have is 3500, the lowest you can have is 0.
Level 1 Missions
Level 1 missions represent the easiest missioning tier and require no reputation. Completing a level 2 mission rewards 10 reputation, failing one loses 50 RP. They have the lowest rewards, averaging about 100 LP per run. The recommended party size is 2. These are easily soloed and intended for use during times when forming a larger party would be prohibitive.
Level 2 Missions
Level 2 missions represent the normal missioning tier and require 500 RP. Completing a level 2 mission rewards 20 RP, failing one loses 100 RP. They have fairly decent rewards, averaging about 200 LP per run. The recommended party size is 4. These are the "normal" missions.
Level 3 Missions
Level 3 missions represent the medium difficulty missioning tier and require 1250 RP. Completing a level 3 mission rewards 50 RP, failing one loses 250 RP. They have higher rewards, averaging about 400 LP per run. The recommended party size is 6.
Level 4 Missions
Level 4 missions represent the hardest missioning tier and require 2500 RP. Completing a level 4 mission rewards 100 RP, failing one loses 500 RP. They have the highest rewards, averaging about 800 LP per run. The recommended party size is 8.