The Scutum is a type of shield in Ryse: Son of Rome.
The Scutum (Scuta plural) was the standard issue shield of Roman Legionaries. Used primarily to deflect weapon strikes and projectiles, the Scutum was an absurdly large shield designed to be used in tight formation, creating an impenetrable wall.
The Scutum is used both as a shield and as a weapon by Marius Titus. The Scuta that appear in-game are actually slightly smaller than the shields normally used in actual history, however this is not inaccurate. Marius uses his shield primarily to bash enemies and break their guard, and sometimes uses it to deliver killing blows while executing enemies. During cutscenes he also appear to push his shield forward and meet incoming blows with momentum of his own to stagger attacking foes with recoil.
Throughout the course of the game, Legionaries are often seen forming defensive lines by aligning their shields and forming walls. When pushing into enemy territory, Marius would order his troops to form on him and create a Testudo (Tortoise) formation— a formation where Roman soldiers align their scuta to form a packed formation covered with scuta on the front and top— to deflect any oncoming enemy arrow bombardments. In Game, the Romans move forward while in a standard line formation and do not cover their top with Scuta until ordered and cannot move while covered.
Scutum on Wikipedia