MISSION THREE - RIMTECH CAMPAIGN

This screenshot depicts a Drilltruck placing an Elevator shaft to be built.  Once completed, any unit may travel down to the underground layer.  Combots are too large to fit into the small underground caverns.  The underground makes for a great staging area for sneak attacks.  Imagine drilling under and enemy base using a Drilltruck, amassing a large underground force and popping up to the surface in a newly constructed elevator shaft next to his base.  It can prove to be a very effective strategy if the enemy isn't prepared.  Another benefit of the underground layer is the Metajoule rich lava pools that can be found there.  Lava pits underground are almost always more rich in lava than any found on the surface.