Description:
A venomous snake bred for experiments, Yawn escaped the laboratory and grew to gigantic proportions after contracting the T-Virus. It was named Yawn by researchers due to the way it opens its mouth when swallowing prey whole. It features a relatively short body when compared to its girth, and its fangs secrete an especially potent venom that can only be countered with a specifically formulated serum.

Notes:
The giant versions of everyday creatures provoke a fear that can't be explained by their size alone—it must be instinctive.
There are a number of memorable in-game moments associated with the Yawn, such as the first encounter with the creature itself and the hunt for the serum after the battle. The Yawn is also associated with the introduction of the surviving S.T.A.R.S. Bravo Team members, Richard and Rebecca—this might be another reason for its popularity.