Zeph observed human society from a distance with great interest before monsters made themselves known. Unfortunately, he was already being tracked by the Open Eyes, and was captured mere months after DISE was formally founded. He spent many years there, subjected to endless cruel experiments.

To his own detriment, Zeph is and always has been very proud, and had a short temper. He fought his captors at every available opportunity, resisted any restraints, and refused to cooperate until he had no choice. DISE agents considered him one of the most difficult and dangerous subjects at that facility, and many dreaded working with him. Any who could successfully subdue or outpace him were granted exclusive bragging rights and the respect of their peers.

Eventually he became too unruly for researchers to study safely with any consistency. Instead, he was submitted for the MA Program, with the logic that statistically speaking, he would most likely die in the field and his remains returned for study regardless. He was matched with Nina, as her superiors were impressed enough by her accomplishments thus far that they wanted to put her capabilities and mettle to the test.

Zeph made it abundantly clear to her from the beginning that he was not going to cooperate any more than strictly necessary for his own self-preservation. Nina had other plans, and "convinced" him to follow orders the hard way. The more time they spent together, the more Zeph came to realize that Nina's beliefs came from a place of misinformation and lack of understanding, not from active malintent. He starts to gradually pick away at her inaccurate beliefs, causing her to grow more sympathetic to him and other monsters and show more of her true self to him. Without the prickly outer exterior, it doesn't take long for him to begin to fall for her.