Description from original post (created 2016-05-30 15:47):
Unlike the Promethean Knight, which are controlled by the composed essences of formerly living beings, Soldiers are purely artificial intelligence-driven. Soldiers have a distinctly humanoid appearance in comparison to other Promethean constructs and Sentinels;
they have one set of arms with small, five-fingered hands. Their main
locomotion is provided by a pair of long, thin legs designed for agility
and speed. Soldiers are covered in patterns of light and have a
fire-like glow inside their heads. In addition, they are capable of slipspace translocation.
Unlike the other Promethean units, Promethean Soldiers are also capable
of speech. The Soldiers encountered in the modern era are known to
taunt their human opponents in English.
Source:http://www.halopedia.org/Promethean_Soldier