The Alien city is a complex organic growth in which each building type functions as a highly specialized "organ". The Megapod Chamber is the reproduction organ of the Alien city which nutures numerous egg shaped structures. These Megapods are giant seeds which grow to a large size before being transported to a new location. The seeds then grow and develop into other Alien buildings. The Megapod Chamber is extremely well defended but once it is destroyed we will be close to victory.
The Megapods are the means by which the Aliens create new structures. The small Egg-like objects are eventually replanted and grow into massive organic structures. Our discoveries are shocking; this building is practically overflowing with Pods. Our Scientists fear that the Aliens are planning a massive expansion and who knows how we could stop them then. All Megapods must be destroyed thus preventing the Aliens building any new structures.
The Megapods are all found in obvious large chambers. The Megapods go up in large explosions when destroyed and will usually chain react around the whole room. This will often collapse sections of the chamber they're in, especially if it's a small one, so try to be outside when they go up.