Giant Dinosaur vs. Mega Snail

HOW TO GET THIS ACHIEVEMENT AT LEVEL 100-110
UNLOCKED AT PATCH 7.1 @ LEVEL 110 WITH GROUP OF 5 PEOPLE

PLAYER REQUIREMENT: Check minimap if your raid is rated for 10/25 Man Mode. If @ 20 Man, you need 10 Players. If @ 10 Man, you need 5 Players. Sometimes jumpy if you place people in group 3-6. Keep everyone in groups 1-2. Possible bug. Worst part about this achievement is getting enough players to help

1. 
   
2. MUST HAVE 5+ PLAYERS FOR THIS ACHIEVEMENT - 5 Players for 10 Man, 10 Players for 20 Man.
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4. Everyone stacks in middle of boss area in one possition. (Mark with world marker)
5. 
   
6. Pull Boss (Anybody). You do not have to DPS the boss at all, until snail is unlocked.
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8. Have everyone get there health down past 50%. As long as its below that, you will get the "Bloodied" debuff from the boss. Once 5/10 or 13/25 Players get the debuff, the boss will transition to phase 2. (You will know when this happens because everyone will get a pushback.
9. 
   
10. You can now heal up everyone past 50% (not required, but recommended)
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12. The boss will now fixate on someone. Typically not tank. Runaway from boss if fixated.
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14. Rotation: A add will spawn. Kill the add. A random person will get the skeleton key debuff. They must go to snail cage (First cage to left @ Entrance) and click on it. Rinse and repeat 3 times and snail cage will unlock.
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16. Run away from boss (if fixated), don't get run over by snail (will one shot YOU) and kill boss.
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18. Once you kill boss, the snail will eat its remains and everyone will get the achievement.
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Garrosh has access to the power of an Old God. No sweat.

Garrosh has an army of Kor'kron and Dragonmaw. No sweat.

Garrosh has Dark Shaman. No sweat.

Garrosh has a Gastropod in a cage.

FOR GOD'S SAKE WHY ARE YOU OPENING THE CAGE? WE'RE GONNA DIE!

How we did the achievement:

- Play the encounter as normal
- In transition phase, focus DPS on Kor'kron Jailers (also range DPS)
- Loot the key as normal, but open the Cage with the snail (the cage on the left when you walk down the floor to Thok)
- Another Jailer with less HP spawns right on the floor, Tank it, move it to the normal kill place, loot his key and open the "normal" cage.
- We did this for 3 transitions and made sure Thok is at ~5% HP before the last transition.
- As soon as you opened the Snail Cage the third time, it will open and the snail will come out.
- It has about 21M HP and will walk right to Thok.
- It will eat Thoks Body after the kill and the Achievment will be awarded some seconds later when the snail reaches the dead body.

As gear gets better, you can maybe do this with 2 transitions and kill the jailer 3 times in the first transition.
We tried to not stand near to the snail - i guess it will eat you right as the gastropods in ToT.
You can find a video from our kill here