What if Caleb had stayed faithful to Phobos instead of becoming the leader of the rebellion? 

In this alternative universe Caleb is an experiment in which Phobos tried to create a more efficient and independent whisperer who was able to learn and think for himself unlike the others of his kind.

 The result was the most ruthless of all of Phobos' whisperers. Caleb is sharp, intelligent and a fast learner, in no time e became the commander of the Prince's guard feared by the Metamoorians, especially the rebels who he slaughtered mercilessly. Leading his troops he nearly brought the whole rebellion to an end and executed most of the opposers of Phobos' regime.