The Aegis is a powerful weapon wielded by Raven. The Aegis is an extremely powerful weapon, but it's abilities aren't offensive.
At some point after separating from Jet Seyre and joining the Legion, Raven acquired this powerful weapon. It's origins and history have never been revealed by Raven. He simply states he "picked it up in some hell." During the Assault on the Citadel, Animus took the Aegis and wielded it himself.
The Aegis is a six foot long claymore with a spiked shield as a hand guard. The end of the pommel has three spikes.
The Aegis, as the name implies, is a shield sword. The Aegis has several abilities, the most notable is the ability to create a shield, either omni directional or a shield wall. This shield is noteable as being one of the strongest shields in existence, depending of course on the user and the energy poured into it.