The Pulsing Egg Sacs look like the other normal egg sacs found around the encounter area, but possess a red effect around them. There are exactly 7 of them located at specific points around the encounter area, some of which can by found on platforms below where the encounter itself takes place. To access these, the Shimmering Feathers spawned during Elerethe's Roc Form phase are required.
The eggs can be destroyed simply by running on top of them, and once all 7 are no more and the boss is defeated, the achievement is awarded.
- Patch 7.0.3 (2016-07-19): Added.