(Big post)
You send the diggers to break down the door. Missiles shoot at the diggers from arrow-slits, but the diggers are quickly replaced, and soon the door falls to the ground with a heavy thud, and the schoolbus moves forward.
The defenders are nothing like you've ever seen. They have two, large eyes on the front of their faces. Their heads are long and oval, and attached to the body by a fairly long neck. The presence of large tuffs of hair near the front of the face covers the mouth of these creatures, while the rhythmic moving of hairs at the top of the head shows where it it breathes. The body is in two segments. The back segment is larger that the front, but is otherwise uninteresting. The front segment has a pair of small wings attached to it, and while otherwise useless for flight, they can be vibrated of communication. Six limbs are attached to the front segment as well. The upper two limbs are designed for grasping, while the back two are for walking. The hand at the end of the limb has three fingers, with the upper two being more finer, while the back two are adapted to allow the creatures to attach to any surface, like a gecko. You know this because several of these creatures jump down onto the back of the schoolbus, and start attacking it. The body of the creatures are covers with fine, oily hairs.
The defenders are armed with swords, hammers, maces and axes, while others have bows and arrows. Their armour is minimal, but they seem to rely on their natural speed to protect themselves.
The schoolbus lurches forward, discharging crabs and the two group being to clash. The crabs clearly have the upper hand in the battle. Their armour protects them from most attacks, and the shrimp claws are much too fast to dodge, and too deadly to be blocked by armour. A few crabs go down, while scores of the creatures are dying like flies. However, the creatures keep fighting till their last breath, making the battle rage for a couple hours. The crabs are easily victorious, and begin to feast on the corpses.
Three tunnels lead from this chamber.
DRONES:
Attack crab drone: Stong, armoured, built to kill. Has incredibly fast, shrimp claws.
Crab drone: Armoured. Good all around. Shoots poison.
Collector crab drone: Make to collect and process DNA.
Light-bulb drone: Gives off light. Fast, but otherwise useless.
Armour crab drone: Highly armoured. Not very fast.
School bus: Carries crabs. Gives of light. Very large and heavily armoured.
Digger: Digs. Otherwise useless.
(We should give a name to these creatures.)