A half-mazoku is a composite being created when a mazoku abandons its natural existence as spirtual being in order to merge with another being, or when a creature is partially transformed into a mazoku by other magical means. In certain cases, it can be seen as some kind of possession.
Half-mazoku possess the extremely large magic capacity of a mazoku, combined with the physical body of a human or another corporeal being. Because they are bound to a true physical form and cannot withdraw to the astral side, they are unable to employ the normal mazoku method of teleportation; they have to resort to the advanced method of "bending space", if powerful enough to do so. However, as they aren't purely spiritual beings, they also lose their limitations on the use of magic. In The Ghost of Sairaag, Copy Rezo successfully casts a spell calling on the power of Ruby Eye Shabranigdu, which would be tantamount to suicide for a pure mazoku.
If the half-mazoku is the product of a merge between a human and a mazoku, the souls of both coexist within the merged being. One or the other may take complete control at times. If the two souls have conflicting desires, then the half-mazoku may hesitate or become paralyzed.
The pieces of Ruby Eye Shabranigdu which were sealed within human souls awaken as half-mazoku. In the cases of both Rezo-Shabranigdu and Luke-Shabranigdu, the human soul within their body was directly responsible for their defeat. Given enough time, a resurrected piece of Shabranigdu could eventually eliminate its human body and return to being a pure mazoku, although what would become of the human soul is unclear.  According to Hajime Kanzaka, it would probably be impossible for any human, even Lina or Luna, to defeat part of Shabranigdu in his pure mazoku form, provided that he could fight them without any distractions. 
- Lei Magnus-Ruby Eye Shabranigdu
- Rezo-Ruby Eye Shabranigdu
- Luke-Ruby Eye Shabranigdu
- Chaos Dragon Garv
- Copy Rezo