Knights-Errant were a secret group of Space Marines, created by order of Malcador the Sigillite – regent of Terra – shortly after the betrayal at Istvan III. These warriors were selected from various legions, loyalist and traitor alike, forming an elite network of operatives for special missions during the Horus Heresy.

Knights-Errant wore grey armor without heraldry, marked only by the Sigilite – a stylized letter “I” with three lines. Their tasks included infiltrations, sabotage, rescue missions, and recruitment for future Grey Knights. Notable members include Nathaniel Garro, Garviel Loken, and Tylos Rubio.

In the Horus Heresy game system, Knights-Errant are not a standalone army but can be part of loyalist forces as special characters. Their fighting style is precise, elite, and narrative-driven – ideal for players who wish to represent Malcador’s “Silent War”.