There are a total of eleven rares on the Isle of Thunder. Ten of them are required for the achievement
Champions of Lei Shen. They are all on very short re-spawn timers that seem to be between 30min to an hour, and certain rares become available after unlocking different Stages of progression on the Isle. (More info on that below.)
All of these rares (minus Ra'sha) share the new tapping system introduced in patch 5.2, where so long as you participate in killing the rare you will have access to it's loot. As more and more people join in on the fight, the mob's health pool will increase with each additional player. All in all, I think this new system is great, as it gives players around the Isle more time to get to each rare once it's been called out.
Each of these rares is guaranteed to drop a
Tome of Valor worth 15 valor points each time you kill them. They will also drop a single
Shan'ze Ritual Stone and a
Key to the Palace of Lei Shen for an individual character once each week (so long as you haven't already looted the key elsewhere). Obtaining three ritual stones will unlock the group quest
Setting the Trap, which will then lead to the weekly group quest
Champions of the Thunder King. Obtaining a Key to the Palace of Lei Shen will unlock the weekly solo scenario
Troves of the Thunder King where you will have five minutes to grab as much treasure as you can before the clock runs out.
These rares also have a very small chance to drop the item that begins the questline for warlocks to get their green fire;
Sealed Tome of the Lost Legion. The tome seems to be roughly a 2-3% drop chance off of any one of the rares (minus Ra'sha), and can only be looted by warlocks. When combined with a Healthstone the item becomes
The Codex of Xerrath, which starts the questline with
An Unusual Tome.
So without further adieu, here are each of these rares listed below in the order they became accessible on the Isle. If you scroll further down the page I also have a slightly more up to date map showing exactly where they can be found.
Haywire Sunreaver Construct
NPCID: 50358
Coordinates: 48, 85
Location Description: Running along the shores in southwestern Ihgaluk Crag
Base Health: 10539k
Notable Loot: Sunreaver Micro-Sentry
Abilities: Haywire: Go Haywire! Deals 18500 to 21500 Nature damage to all enemies within 40 yards every 1 sec. for 20 sec and increases movement speed by 100%. (
Ranged players can still dps him and not get hit, so long as you stay right at about 40 yards. Others should be able to heal through it. If you don't have heals, I recommend getting away from him for the 20 seconds he casts this.)