The Vayeate is one of two experimental mobile suits created for OZ by the five scientists who developed the Gundams. Forced by their captors to create a weapon that can defeat a Gundam, the scientists devise a pair of mobile suits - one offensive, one defensive - that can fight as an unbeatable team. Whereas the Mercurius was designed as a defensive mobile suit, the Vayeate was designed primarily as an offensive unit. Since the Vayeate was intended to be as powerful as the infamous Gundams, OZ selected one of its own pilots, an extremely capable young man named Trowa Barton to be its test pilot. Months later, the rebel army White Fang uses Trowa's recorded pilot data to create an unmanned mobile doll version of the Vayeate.

Designed strictly for maximum firepower, the Vayeate is armed only with a powerful beam cannon, based on the Wing Gundam's buster rifle. This cannon was designed to provide a damaging blow almost equivalent to that of the XXXG-01W Wing Gundam's powerful buster rifle. To overcome the problem of the buster rifle's limited charge, the scientists designed a large energy collector connected directly to a generator on the mobile suit's back, providing the Vayeate's beam cannon with a virtually limitless "ammunition" charge. Note that both the Mercurius and Vayeate have a visor that protects the mobile suit's vulnerable sensor plate.

Source: Gundamproject.com, New Mobile Report Gundam Wing