Cooperative Loot System

The Cooperative Loot System, also known as Participation System, is a loot distribution method introduced with the Summer Update 2013. This system allows loot from Bosses and some event creatures to be distributed among players in a more fair way than the classic loot system. 
Whenever a player get loot from this system, the items will be found inside a Reward Container, which can be accessed from the creature's corpse or later at the Adventurers' Guild in the Reward Chest.
== Participation Rules ==
Note: CipSoft has chosen to not disclose details about the Participation Rules of this system, and the information presented here is based on observation made by players. 
The loot obtained from the bosses with Coop Loot depends on each character's participation in the fight. On most cases, the participation is relative to the other player's contribution, however, in certain cases there may also be a minimum participation, as discussed below. 
Participation can be earned in three different ways:
# Dealing damage to the boss;
# Receiving damage from the boss;
# Supporting other players during the fighting by e.g. healing.
The exact weight of each source of participation is unknown, and it's possible that different bosses have different weights. This means that for a certain boss, dealing damage could be the most important factor, while on others healing could have a high impact. 
=== Participation Tiers ===
Most bosses in the Coop Loot system have at least two Participation Tiers, with different (apparently cumulative) loot tables. The rules for each tier vary a lot from boss to boss. Certain bosses have tiers which will only be reached by a limited amount of players, in some cases, by a single player. 
The first tier usually has very poor loot, sometimes with only one item such as a gem. Players generally only fall in this tier when they don't actually participate on the fight. For example, if they only hit the boss a few times with weak attacks, while the other players spent several minutes attacking the boss with full strength. 
The second tier of loot is where most players will fall in most bosses. Quest bosses usually have only these two tiers, and the rare loot players are looking for have a small chance from being obtained by everyone in this tier. In these cases, the chances of looting the rare items are independent for each player, which makes it possible for two or even more players to get rare, even identical, items. As an example, it's not rare to see a "double loot" like this from the Dream Scar bosses, since their "rares" aren't very hard to drop. 
There are also bosses with higher tiers and better rewards, which are limited to a certain amount of players with the highest participation score in the fight. The most classic example is Ferumbras, which will always drop one Ferumbras' Hat for a player. Despite observation from many players over the years, it's still unclear whether the Hat will always go to the player with higher participation (usually the highest damage dealer) or if it's raffled between more than one player that reaches the minimum participation to reach the higher tier. 
One boss where the participation system can be clearly seen in effect is Gaz'haragoth. This boss has 4 different participation tiers, with the following loot possibilities:
# 100% chance of getting all Blessing Charms and usually a Crystal Coin, a Cluster of Solace and a Dream Matter.
# All the items from tier #1, as well as more Clusters of Solace, potions of all kinds, creature products, gems and other common items. 
# Items from the previous tiers and a 100% chance to get one Crude Umbral item. 
# Items from the previous tiers, one Regular Umbral item, one Umbral Master item and a Nightmare Horn.
== Abuse Case ==
Due to how this system can reward players just for interacting others players involved in the fighting, by healing or using potions on them, there was a period when players tried to massively abuse this system to get rewards from bosses without actually fighting them directly and consuming their cooldown.
On January 4, 2019, it became widespread knowledge that if you healed or used a potion on a player that had just participated in a fight against Coop Loot bosses before it was killed, you would also receive participation in the fight. This was easily proven with Grand Master Oberon, since by using this method players would get the Millennial Falcon achievement and a reward bag with the The Spatial Warp Almanac, which is a 100% drop from the boss. Assuming this also meant there would be a chance of obtaining Falcon Set items by this method, players accross several worlds started to abuse the reward system.
The method consisted of entering the boss battle with two or more players and fighting up to the last stage, when at least one of the players would leave and run to a place with many other players, or even suicide for a quick trip to the temple. There, other players would heal or use potions on the character that had fled the battle, and after a while Oberon would be killed by the those who remained in the boss room. Using this method, even level 8 characters could "join" the fight and gain participation. 
Using the same strategy, players also farmed the loot from The Percht Queen, which at the time had guaranteed drops of Silver Tokens and Gold Tokens.
The following day, on January 5, CipSoft released an on which the access to Grand Master Oberon was closed until further investigation. It was later disclosed that on this patch the Tokens were also removed from the Percht Queen's loot. Two days later, a news with a report about this incident was . The conclusion of the investigations by CipSoft were:
Initial investigations and further in-depth analyses, however, could not substantiate the reports about an increase in falcon item drops or other rare items from various bosses that distribute their loot based on a participation system.
Regarding The Percht Queen, however:
An exception is the Percht Queen from the Winterlight Solstice Event. Diagram Tokens & Soul Stones shows an increase of gold and silver tokens since the beginning of the event. We deeply regret the problems resulting from this.
The access to Grand Master Oberon was restored two days later, on January 9. Even though this led to no direct changes to the reward system, there have been no other reports of similar abuses since this event.