This, like so many things, is basically HP's fault.

On the Twelfth Day of Halo Christmas, Bungie gave to me:

Twelve Drones a-droning,
Eleven Jackals sniping,
Ten Brutes a-battling,
Nine Helljumpers jumping,
Eight Elites ejecting,
Seven Scorpions shooting,
Six Grunts a-sleeping,
Five sacred rings,
Four Flood combat forms,
Three Prophets,
Two dead Hierarchs
And a personality construct in the Core.