Mvp
For some events on Zeah, loot is rolled uniquely via the MVP system. This system effects the Corporeal Beast, Nex, and all 4 GWD bosses. The purpose of this system is to make these masses worth attending for every, as the best geared people won't just be snagging all the rare drops. EVERYONE will roll for non rare drops every kill.
The player who dealt the most damage to the boss will roll a flat chance of 1/20 to be the MVP. If the highest damage dealer should fail the 1/20 roll, everyone (including the top damage dealer) will roll an equal chance to be the MVP for that kill. An additional MVP will be rolled for every 10 players at an event. This acts as such to ensure players have an incentive to come to masses, even if they're not the top damage dealer. It also rewards the top damage dealer slightly, by offering them the initial 1/20 roll to take MVP.
Examples:
There is an event for Corporeal Beast, 8 players are there. Arcadia has dealt the most damage and gets the 1/20 roll for MVP, they fail the roll. All 8 players now roll a 1/8 chance to be MVP, this player is able to have a chance to roll on the very rare drop table.
There is an event for Nex, 18 players are there. Arcadia has dealt the most damage and gets the 1/20 roll for MVP, they fail the roll. All 18 players now roll a 1/18 chance to be MVP, this will happen twice since there is an additional 10 players, these players are then able to have a chance to roll on the rare drop table.
The Nightmare uses the same drop mechanics as OSRS.