Androids are a complex type of humanoid robot. All surviving androids were created by inventors Martin McFarlane or Gabriel Alchemilia centuries before the events of The Demon's Light. Several of them appear throughout the series.
Centuries prior to The Demon's Light, inventor Gabriel Alchemillia built a group of functional humanoid robots that took on human qualities. Gabriel became a world renowned inventor due to this creation. Years later, his friend, Martin McFarlane, took Gabriel's blueprints and betrayed Gabriel and his team of Alchemists. Martin created similar androids, and both Marty's and Gabriel's Android's are malicious.
Androids have metallic bionic skeletons underneath their skin, which can range in color from white to black, similar to humans. Their skin is in fact a metal cloak that can, theoretically be removed. Often, androids dress in human attire.
Each of Marty's androids come equipped with micro-chip contained abilities that vary from one android to the next. However, all of his androids have nose sensors, weapons, and back-up limbs. They are also all vulnerable to water. They are the one of the most intelligent species on the planet, due to all having minds made of computer devices.
Gabriel's androids are very similar, though none of them have been killed to see their exact internal structure.