Black Dragon Egg

In Ulthuan, the egg of a Dragon is sacred, and harsh punishment awaits any who endanger or disturb a Dragon nest. In Naggaroth, a Dragon egg is naught but a potential source of power, and their nests nothing but cradles to nurture that power. So it is that for every Black Dragon Egg that develops into a hatchling, countless dozens more are taken and consumed, so that their devourers might take a portion of the eggs' strength as their own. 1a

Source
Warhammer Armies: Dark Elves (8th Edition) -- pg. 62