Weddings are important events. In the times depicted, the fate of nations, political alliances or wealth distribution amongst nobility were among many things that weddings were useful for.
There is also the pressure of time and the quirks of the nobility at play. The bride to be, broke her leg - something she will recover from, but there is no time to wait for it. The enemies of the noble house are in motion and stabilization and alliance is needed. Someone has to marry the groom... like someone who specializes in replacing and impersonating people. Someone who dons a skin to achieve the effect. Enter the Masters of Deception, an ancient, powerful, secretive guild selling their services to the highest bidder - their business is imitation at the highest level. The groom will notice nothing.
Best wishes to the happy couple! <3