This is a posable action figure from the Nendoroid series.
From the Good Smile Company website:
From the popular browser game "Millennium War Aigis" comes a Nendoroid of one of the princesses, Sybilla! She comes with three expressions including a standard expression, an expression for combat as well as a damaged expression.
Her sword is included and can be displayed both sheathed and drawn with different parts, allowing the Nendoroid to take all sorts of action poses from the game! Be sure to add the selfish Princess to your collection!