Half-modrons are, to our knowledge at least, magical creations. In appearance, they tend to be similar in appearance to a prime race called Mechalus, although, it totally depends on the non-modron component of the union. They are not Modronoids (a type of cyborg) or a machine that resembles humans, but a true union of humanoid and automaton. It is not known whether half-modrons can reproduce with each other.
Half-modrons, if they see the light of day and are not confined to a deranged magician's laboratory, will normally try to hide their heritage as they are afraid how either society would react. Half-modrons display a variety of behaviours, depending on the characteristics of their parents (they might even have been created from rogue modron stock!) and the degree to which they resemble each side. If half-modrons recognise one another, they tend to stick together for mutual support.