Caleb

 was a humanoid abnormal that was leader of the Hollow Earth insurgence and was considered to be "Public Enemy number one".

Caleb met with Dr. Helen Magnus saying he wanted to end any hostilities between the Hollow Earth abnormals and the human race. Caleb wanted to build a new homeland for his people on the surface in Old City's Fifth Ward. Magnus was happy to help the Hollow Earth abnormals build a new home and gave Caleb the Sanctuary's full support.

It was discovered Caleb wasn't hoping to create a future where humans and Abnormals could live together; Caleb wanted himself and his people to be rulers of the human race. Caleb created a virus from the source blood that was stored in Praxis before it was destroyed; his plan was to release the virus and infect every human on the planet. The virus would awaken the dormant abnormal genes in human DNA causing severe mutations thereby turning every human on the planet into an Abnormal. However, Bigfoot stole the virus from Caleb before he could unleash it and brought it to Magnus.

After killing Bigfoot, Caleb and a small group of fellow Hollow Earth abnormal insurgents went to the Old City Sanctuary to kill Magnus and take the virus back. However, Magnus was able to kill Caleb, his team, and destroy the Sanctuary before he could get the virus and kill her.