I'm not quite sure how to put this, but I'll give it my best effort: Listen here, you insane, befurred woman! That's a King Egg! 
The King Egg is a bioweapon designed by the Kree to control the Brood. It usurps the Brood's natural hierarchy by giving one member a supercharged version of the Empress' pheromonal control for 5–10 standard Kree cycles. 8,000 years after its creation, Broo consumed the King Egg and became the first Brood King.[5][6]
History
Approximately 8,000 years ago, an imperial team of xenotomologists of the Kree Empire first encountered the Brood. After witnessing the adaptive and aggressive nature, the Kree began to plot how they could weaponize the Brood. To gain control over the rival matriarchal hives, the Kree scientists created the King Egg, a patriarchal element that would disrupt the standard Brood breeding cycle and unify the Brood under a singular king. The Supreme Intelligence approved of the plan, but also calculated that it would take no less than eight millenia for the Brood's hive society to possess a sufficient volume to effectively topple the Kree's rival empires.[5]
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Wolfsbane stealing the King Egg
Recently the Starjammers were hired by a Kree Accuser to retrieve the King Egg from Benevolence, a Shi'ar outpost on the border of Brood territory. However, the Starjammers' passengers, the New Mutants stole the egg first with Wolfsbane hiding the egg inside Mondo, leaving the the Starjammers with an empty container.[2]
When the New Mutants returned to Earth, Wolfsbane placed the King Egg in the ALPHA House where Broo recognized it just before a Brood-controlled Acanti crashed into Krakoa. With the help of Jean Grey and Cyclops, Broo was able to get the egg off Earth.[3]
Escaping in their Shi'ar Scout, the X-Men were able to reach Shi'ar space before being overtaken by the Brood. As the Brood closed in, Broo ate the King Egg becoming the king and ruler of the entire Brood race.[5]
Some Brood hives appear to be able to resist Broo's control.[7]Properties
Brood Dominance: A King Egg disrupts the Brood breeding cycle and places all Brood (including rival queens) under its thrall. Unless special precautions are taken, Brood hives can smell a King Egg from across the galaxy.[3]
See Also
- 4 appearance(s) of King Egg
- 2 minor appearance(s) of King Egg
- 3 mention(s) of King Egg
- 5 image(s) of King Egg