In this chapter, the player meets Xenian enemies for the first time, such as the Headcrab, Zombies, Houndeyes, and Barnacles.
Due to the great number of scientists in Anomalous Materials before the incident, the player will find a great number of zombies in Unforeseen Consequences (specially in areas where they aren't found in Half-Life, like the lobby). The combat with them is intended to put more action between the long periods of level exploration.
