Shroud, the artist formerly known as Giga.
Shroud's pilot is Phil Besaedas, and it is a custom S grade FORTRESS class Craft, Anti-Ground Conqueror Series 12 (AGCS - 12). The purpose of FORTRESS types is to be missile mules and frontal assault fodders that take damage for units behind them. These units are the most common and most destructive of ground Crafts.
The name Shroud is given to this unit by Phil and his comrades due to Phil's protective strategies in combat, which saved the lives of many soldiers and pilots. Hence his title "The White Knight".
The extra set of limbs on this unit is detachable. Removing the limbs and attaching lighter arms on this unit transforms it into a VALKYRIE class. Attaching land cruiser leg parts and light assault attachments transforms it into a LANDSHARK class capable of high speed ground combat.
The attachment seen in this concept contains Heavy Assault Rifle with Pilum missile shoulder attachments. It travels up to 80 to 90 kph on flat terrains. It also possess back boosters and under boosters which helps propel this unit through the terrain and assist in executing sudden turns. It can detach its arm rifles and missile pods after ammo has been depleted to reduce weight. It can also detach its extra set of limbs during combat.
This unit disappeared with Phil after his last defeat in a mission to annihilate Stratus and Shadow. The wreckage of his comrades' Crafts were found but Shroud was missing. Archamel database shows that Shroud was last spotted in a raid against an Archamel friendly mercenary group, in which Shroud led the charge along with Stratus and Shadow.
Cuz' in Gundam, they never run out of bullets/missiles.
So, anyway, good job.