Crossbow, Hand: You can draw a hand crossbow back by hand. Loading a hand crossbow is a move action that provokes attacks of opportunity.
You can shoot, but not load, a hand crossbow with one hand at no penalty. You can shoot a hand crossbow with each hand, but you take a penalty on attack rolls as if attacking with two light weapons.
Crossbow, Heavy: You draw a heavy crossbow back by turning a small winch. Loading a heavy crossbow is a full-round action that provokes attacks of opportunity.
Normally, operating a heavy crossbow requires two hands. However, you can shoot, but not load, a heavy crossbow with one hand at a -4 penalty on attack rolls. You can shoot a heavy crossbow with each hand, but you take a penalty on attack rolls as if attacking with two one-handed weapons. This penalty is cumulative with the penalty for one-handed firing.
Crossbow, Light: You draw a light crossbow back by pulling a lever. Loading a light crossbow is a move action that provokes attacks of opportunity.
Normally, operating a light crossbow requires two hands. However, you can shoot, but not load, a light crossbow with one hand at a -2 penalty on attack rolls. You can shoot a light crossbow with each hand, but you take a penalty on attack rolls as if attacking with two light weapons. This penalty is cumulative with the penalty for one-handed firing.
Norfleet said:I'm not sure what use this would be, other than the ability to discharge them both on round 1, drop them, and quickdraw something else. To continue to use two crossbows would be two MEAs to reload both of them, which would consume your actions for the next round.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.