On the technical side of things, every rare creature (and potentially some elite creatures) on Island Expeditions has a loot table. However instead of being able to loot the creatures directly after killing them on Island Expeditions, the results of those rolls at the loot table is calculated at the end of the Island Expedition.
This means the most effective way to grind special Island Expedition rewards is to seek out named rare NPCs around the Island and also kill a few varying types of creatures (instead of farming the same types of elite creatures). However, due to the score limit, this also means that looting Azerite from chests, mining nodes, or the Unbound Monstrosity elemental event is counter-productive to collecting rare rewards as they only end the Island Expedition faster and give you less time to search out other rare creatures.
When looking to target certain rewards, there are two systems of Island Expeditions that exist to help encounter a lot of a certain type of creature.
Note About Invasion Events: Currently, invasion events are much easier to trigger on lower difficulties of Island Expeditions
- Island Creature Theme: The 3 Islands every week will also come with a creature theme shown on the Expedition Map interface when queueing for Island Expeditions. The creature themes associated with each Island are also shown in the "Today in WoW" section on the Wowhead homepage! This means you will often encounter these types of creatures when on an expedition to that particular Island, giving you many opportunities to get rewards associated to those types of creatures. So when Rotting Mire contains Pirates for the week, expect chances at Gracchino after every Island Expedition to Rotting Mire.
- Invasion Events: The 2nd is the Invasion event that occurs during some Island Expeditions which occurs as teams collect Azerite around the Island. An invasion event causes a lot of enemies of a particular theme to spawn on the Island, giving many creatures of a similar theme for players to kill to add a lot of rewards around that theme to their loot tables. So when a Vrykul invasion occurs on your Island, expect a decent chance at many Vrykul themed items such as Lama dei Re del Nord Saccheggiata.
, but it is unclear if the difficulty of Island Expeditions has an effect on the chance
at some Island Expedition rewards. Invasion events are explained in more detail in our Island Expeditions: Random Events and Invasions