Each alien has different strengths, abilities, and of course, weaknesses. This demands the use of a variety of tactics in approaching the different foes. The Artificial Intelligence behind these monsters in Marathon 2 is solid. The monsters do not just mindlessly attack you head-on, but often strike in concert from multiple angles. They employ hit and run tactics, using their ranged weapons with deadly accuracy and then disappearing into the shadows.
Ambushes seems to be another popular tactic among the aliens.
More than once I have been caught off guard by a pack of mutant hiding underwater, motionless, and therefore invisible to my sensors. You will soon find the pistol you start out with ineffective and childish as you battle some of the tougher enemies. Luckily, there is a variety of weaponry to find and use in the game. Some of these weapons, such as the rocket launcher and the shotgun are pretty much standard throughout the genre. While others such as the fusion pistol are more exotic.