Amy Howe has been successfully hybridized with a leafcutter bee.

Amy is petite, abnormally so. Her hair is an unusual yellow and brown mix, much like the bodies of some bees. Her hair color happened after she made her transition from fully human to human hybrid. 

Amy also wears fine down over her entire body, although you only notice up close. The hair is not really hair but a sensory organ that allows Amy to be hyper-aware of everything going on around her using air pressure and temperature to define her surroundings even in the dark. Amy's eyes sparkle with miniature green crystal-like formations. She can see individual images through each crystal in her eyes.

Amy is friendly and effervescent with everyone she meets. She has a slight buzz when she talks (her bee heritage!) and a slightly sweet (and pleasant) aroma similar to honey. Although her left arm is slightly shorter than her right, Amy is bothered more by her short stature. She had hoped to grow taller through inclusion in the Tower's human-hybrid project and has yet to accept that it will never happen.

We first meet Amy in Book 2 of The Human-Hybrid Project, Inside the Darkness.

Marina Bruni is Marisa Bruni's older sister.

Marina looks like Marisa, although with several distinct differences. Marina is a failed hybrid. She is fully functional as a person, but she exhibits scales on her neck, has vestigil gills, and the right side of her body displays a successful transformation to aquatic capabilities. The left side appears normal. At first, Marina's hybridization seemed to have failed, and she worked in the upper levels of Corona Tower. Once her changes became too obvious to hide, she was assigned to Basement Level 3 to live in the quarters assigned to failed hybrids (the ones that can still function independently). Marina refuses to acknowledge her aquatic adaptations, and she keeps her body turned to hide them. One drawback to Marina's failed transformation is that she must spend at least an hour a day partially submerged to hydrate her skin. Moisturizing creams can extend the time she can be out of water but are only a temporary solution.

We learn of Marina's existence in Book 1 of The Human-Hybrid Project, but we first meet her in Book 2, Inside the Darkness.

Marco Lopez is a failed hybrid, but not because he cannot do everything his hybridization promised.

Marco's change went too far for him to be disguised as still human when his DNA was joined with that of a lemur.

Marco has a lemur's large bright eyes, but his most distinguishing characteristic is a large tail for balance. Marco can scale anything. If he can get a grip, he can climb it.

To Marco's embarrassment, he has also taken on the scenting characteristics of a lemur. Flowers are also especially tasty to Marco, so anyone who sets out blooming plants around the facility knows to warn Marco to keep away (although if the flowers have a strong scent, good luck there).

By design, Marco continues to evolve, with his face and body taking on a more lemur-like form as time passes. Marco has set himself a challenge: to stop marking the research facility with his scent. He doesn't know if he can be successful, but he vows to try.

We first meet Marco in Book 2 of The Human-Hybrid Project, Inside the Darkness.

Justin Kurtew is normally seen in a leather duster. 

The duster is to hide certain changes to Justin's body. He has been unsuccessfully hybridized with a praying mantis. He has an extra joint in his forearms making his hands whiplash quick. He can retrieve a knife and kill an opponent before they even know he has drawn it.

Justin tends toward combative interactions with other people. Like a mantis, his temptation is to dismember and eat his victims. The worst thing possible is for people to cheer him on. It releases in him a killing instinct that quickly spirals out of control.

Justin lives on Basement 3 level with the unsuccessful hybrids.

We first meet Justin in Book 2 of The Human Hybrid Project, Inside the Darkness.