Planet of Origin: a world orbiting the star system Lalande 21185, 8 light years from Earth.
The Caxtarids are humanoids with metallic red hair and glowing red eyes, although exceptions are known to be green instead of red. They developed an aggressive and expansionnist space faring civilisation. Caxtarid Corporations are known to have conquered Kapteyn 5, home of more than sixty sentient kapteynian species including avians and butterfly people and have strip-mined a dozen inhabited worlds.
They were wiped out in the 26th century by a biological weapon they wanted to used against dissidents to the regime which went out of control destroyed DNA. They were experts in the creation of living torture machines and known for trading slaves.
Source: Doctor Who universe, Virgin New Adventures novels Return of the Living Dad and The Room with No Doors, both by Kate Orman and Eighth Doctor Adventures novel Seeing I, by Orman and Jonathan Blum.