Drinol

The Drinol are Covenant beasts that did not make it into Halo Combat Evolved, Halo 2, or Halo 3, and it is unknown if they will be seen in future products of the Halo universe.

In the Behind the Scenes DVD, Drinol are described as huge beasts that are kept contained and segregated from the other forces. Possessing phenomenal strength, they are often used to smash enemy vehicles.


 * --Gamesradar article

Marathon Connection
Bungie enjoys placing links to their previous game franchise Marathon into Halo.

From a description of an enemy in Marathon:

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They appeared in two levels in Marathon, and seem to be slow as mentioned above but also unintelligent. With spike-like organs on its skin. The Hulk is pure muscle and has to eat often.