These phantoms from the Underworld have no bodies to speak of–they're given shape by the pieces of armor they wear. When Sonic runs across one of these footsoldiers, he never knows what kind of threat he's facing, as their weapons, tactics, and roles vary. — Description, Sonic and the Black Knight US website
The Soldier-Ones are humanoid creatures. They are covered in full-body purple and gray armor resembling that used by medieval knights which has orange-yellow medieval markings around the torso and the shoulder blades. Behind their helmet, they have a single eye. The inside of their armor however, is completely empty.
The Soldier-Ones primarily attack the player with either horizontal or vertical sword swings, or by jumping into the air and swinging their swords down on the player, though these attacks do minimal damage. When not using their swords, the Soldier-Ones charge into the player with their shoulder (their shields when they have them) which will knock the player backwards, but not damaging them.
Easy to dodge and defeat, the player can destroy a Soldier-One with just one sword slash. However, in some cases, they are equipped with shields which can protect them from upcoming frontal attacks, though these shields will eventually break down when hit with enough attacks (the shields of wood are the weakest while those of metal are the strongest).
Powers and abilities
The Soldier-Ones are able to teleport to different locations by emerging from black voids. They also have impressive jumping abilities, allowing them to jump several meters into the air.
According to Caliburn, the Soldier-Ones are full-fledged knights, suggesting they possess a high level of fighting skills. They have each a respectable level of skills in swordsmanship and shieldsmanship, being able to use both swords and shields offensively with proficiency in combat.
The Soldier-Ones, as their name suggests, each wield a Cursed Longsword which they use as their main offense. In some cases, the Soldier-Ones also wield large shields, made from either wood or metal, which they use for both offense and defense.
↑Sonic Team (March 13, 2009). Sonic and the Black Knight. Nintendo Wii. Gallery. Vault 1. [Enemy 01] "Image of the Knight of the Underworld, a Soldier-Ones. There appears to be nothing inside the armor."