Amon is a strange character in this show, he spends alot of his time sulking and being moody if you ask me, grumpy sod lol. But he is charged with being Robin's parnter, to train and teach her to be a hunter. He isn't pleased about doing this, being a grumpy sod lol. yet he does help Robin on several occassions through out the show, like for example giving her glasses so she can control her power. Which is very unusual, maybe he does soon discover he has small feelings for Robin??. Also in his past Amon hunted his previous Partnet as a witch...but why?, she was a partner and now a witch?. the enemy?
This is due to the fact that his mother wasa witch and when she was hunted it seperated his family. After SOLOMON attacks STN-J to catch Robin he helps her escape and also puts her in touch with his half brother Nagira, for food and shelter.
Amon it turns out inherited the witch gene from his mother yet his abilites have not yet appeared, unlike his half brother as they do not seem to share the same mother only the same father.
At the end of the series Amon seems to disappear with Robin, this suggests they together might help remake the witch race as Robin's father Toudou wanted, is amon the Adam of the witches?. I dunno. Or maybe they both died in the explosion of FACTORY?