The Battle of Riovanes Castle is a battle in Final Fantasy Tactics between the Knights Templar and Knights of Riovanes that takes place in Riovanes Castle during the War of the Lions, though the two are not directly related. The battle takes place in the aftermath of the Knight Templar raid on Orbonne Monastery, in which they attempted to recover the Virgo Zodiac Stone and the Scriptures of Germonique. While they succeed in claiming the stone, the Scriptures fall into the hands of Ramza Beoulve, and Ramza's sister, Alma Beoulve, is captured and brought to the area around Riovanes Castle.
The conflict begins with the Grand Duke Barrington capturing Isilud Tengille while the Knight Templar is carrying the captured Alma through the Duke's territory. The plan was to use Isilud and the Zodiac Stones he carried as leverage to bring the Knights Templar—whom Barrington considered the greatest power in Ivalice—under his control.
However, when Folmarv Tengille and his fellow Lucavi, Wiegraf Folles, come to negotiate at Riovanes Castle, the leader of the Knights Templar is not willing to compromise even for his son. Instead, Folmarv transforms into Hashmal, and, along with Wiegraf, they slaughter the castle guards.
Meanwhile, Ramza and his party, along with Rapha Galthena, head to Riovanes to take Alma back when they are confronted by the Guards lead by Marach Galthena. After a skirmish outside at the castle gates, Rapha and Marach both flee and the gates open as a dying Riovanes knight tries to call for help.
Inside the castle, Ramza engages against Wiegraf in battle. Despite Wiegraf's powers as a White Knight he is still defeated. Wiegraf transforms into Belias, the Gigas, summoning several Archaeodaemons to aid him. Ramza brings his own forces to his aid, and the two sides battle. Belias is destroyed, and Ramza takes possession of the Aries Stone.
Alma listens to the chaos outside her prison cell with fear. A fatally wounded Riovanes guard enters her room for safety, only to succumb to his wounds after warning her to flee for her life. Trying to escape the madness, Alma makes her way to Barrington's chambers, where she finds Isilud fatally wounded—murdered by his own father for his weakness. Folmarv enters, and with the Virgo Stone is able to find that Alma is in fact the perfect host for Ultima. With her in his possession, Folmarv leaves Riovanes to continue the Lucavi plot.
Ramza and his party proceed to the roof of the castle where Barrington has fled to escape. Rapha attacks Duke Barrington, where he admits to raping her. Marach hears this and betrays Barrington to aid Rapha, blocking a bullet for her and himself becoming fatally wounded. Then the Marquis Messam Elmdore shows up with two Assassins, Celia and Lettie, revealing themselves to be Lucavi in league with Folmarv. They kill the Grand Duke by throwing him off the roof, but are injured by Ramza's forces and forced to retreat.
Marach lies badly wounded, and as his life slips away, Rapha stand over him with the Zodiac Stone in hand. A voice tells her to use the stone to save him. Ramza, remembering how Wiegraf was taken by the Lucavi, warns her against it, but Rapha listens to the voice. Her brother is resurrected by the light. Both join Ramza's party afterward.