|Colour Scheme||Legion Info||Symbol|
|Alternative name:||The Dauntless|
|Colours:||Red & White|
One of the most ancient Legions of Mars, they were among the first Legion's targeted by traitors in the Schism of Mars. During the Death of Innocence the Legio Fortidus, along with the Legio Agravides, were destroyed when their reactors went critical, annihilating their fortress and much of the Erebus Montes.
- Bastion of Sorrow - Warlord Titan, destroyed during the Battle of Molech.
- Hound of Mars - Warlord Titan, destroyed during the Battle of Molech.
- 1: Mechanicum (Novel) by Graham McNeill, Chapter 2.06, pg. 282
- 2: Vengeful Spirit (Novel),[Needs Citation]
- 3: Adeptus Titanicus: Doom of Molech pg.20