There is only a single achievement in the Stonecore called Rotten to the Core and involves the very last boss, High Priestess Azil.
At first glance this achievement seems difficult, after all collecting and holding 60 adds involves a lot of coordination during the fight. Seeing as they spawn semi-randomly and can agro against anyone, get killed easily by the AOE in the room and it makes it very complicated.
However once you realize that there are exactly 60 followers standing around in front of the High Priestess that are normally cleared before engaging her and the achievement becomes very simple indeed.
How you should deal with this fight is engage the boss as you run in to aggro the adds. Make sure the boss is in the fight before killing the adds though. Once the boss is engaged and the adds are on the tank all AOE should put on the adds as quickly as you can. Ideally, a Heroism / Bloodlust and then a frost mage can nova them into place and hold when while all AOE hits them repeatedly. During this time everyone other than the tank can just ignore the boss.
Once all the adds are killed you will earn the achievement, even before you beat the boss. At this point you can either fight the boss, if the group is in any shape to, or wipe it up and come back for a clean start on the boss.
Please note that if you choose to do the achievement in this manner, you will only have one attempt, as the adds will be gone for any further attempt.
You can return the to main guide page here: Glory of the Cataclysm Hero Achievement Guide.
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