Firenze's band is a band of centaurs who live in the Forbidden Forest. The group is connected to the colony of centaurs in the forest and is also very respectful of the traditions and centaurs. However, the band is extremely hated by Bane and his alida, who didn't accept the return of Firenze the colony.
Firenze: "Are seeing. I said that focusing the light from Venus to the east was the sign of someone in danger." Rubeus Hagrid: "How would they get here?" Firenze: "An unusual light on Venus focusing on the east was the sign of someone in danger." Scorpius Malfoy': "We already know that!"
— Firenze explains the lights of the stars after saving Albus, Scorpius and Hagrid of the Acromantula's attack.
Firenze's band appeared at the site of the ambush when a spell of Scorpius cleared the area and caught the attention of the centaurs. When they arrived on the scene, Firenze killed the acromantula Moragog and then gave support to Malcolm Baddock who was near death, especially Varenze, the healer of the band.