Hammon is the Ark's lead Gearhead (engineer). As Bormin describes him early in the game, without Hammon, there is no Ark. He is the person who keeps everything running and working. Without his machines, the survivors on The Ark would not last very long.
Hammon is known to deep into the Zone, looking for machines to help The Ark and it's inhabitants survive. He often has to travel farther than anyone else has ever dared to go to find what he needs.
Early in the game The Elder has discovered that Hammon has taken a team and traveled deep into the north end of the Zone. While that alone is not unusual, this time he didn't come back. Panicked, The Elder meets Bormin and Dux at the elevator during their return from the Zone and asks them to head back out and find Hammon.
It is later discovered that Hammon and Magnus were ambused by the Nova Sect who learns of Hammon's ability to 'talk to machines'. They leave Magnus to die, but take Hammon with the intent to force him to "interpret the gifts of the Ancients and open the gates to Eden ". Once the gate is open, the Nova Sect intend to blow up the Zone, taking The Ark with it.
- It is mentioned in a cutscene that Hammon is a mutant with the ability to understand/communicate with a machine, his exact ability could possibly be psychometry