"Mantle vs. Sabyrs" is a battle that occurred in "The Greatest Kingdom" as Team RWBY, Jaune Arc, Nora Valkyrie, Lie Ren, Qrow Branwen, Oscar Pine and Penny Polendina defend the city of Mantle from an attack by several Sabyr Grimm.
After Ruby Rose and her crew land in Mantle to evade being arrested for stealing an airship, Maria Calavera takes them to Pietro Polendina, who fills them in on the state of James Ironwood and Atlas after the Fall of Beacon. He then recognizes them as Team RWBY and comments how his daughter has told him so much about them. Before the group can question him about this, alarms start blaring, indicating that Mantle is under attack by Grimm.
Barreling through the streets and taking down all the Atlesian Knight-200s that try to oppose them, many Sabyrs charge at Team RWBY, JNR, Qrow and Oscar. Yang Xiao Long charges in first followed by Ren. Not wanting to be left behind, Nora looks at a confused Jaune and uses him to boost herself of his shield. Together, Yang, Ren and Nora take out their first Grimm as the rest follow their lead.
Immediately, Jaune slashes and kills the first Sabyr that approaches him and blocks the attack of a second one before stabbing it into the side to finish it off. Following Jaune's attack, Qrow kills two that try to pounce him, transforms Harbinger into its scythe mode to kill a third that tries to attack him from behind before punching and spearing another that tries to kill him from the front and slices the last Sabyr charging at him.
Qrow then decides to continue shooting at the other Grimm while another behind him charges at Oscar. Oscar jumps over the Sabyr and kills it midair while Ruby snipes one that tries to attack him from behind.
Transforming Crescent Rose into its scythe mode, Ruby charges through the Sabyrs, killing three of them while accelerating, before she throws her weapon through the air and jumps off another Sabyr to slam her scythe into the ground with massive force.
As Yang kills a Sabyr, she fails to notice another one charging at her from behind. Blake Belladonna protects Yang by shooting it, which leaves her open to attack by another Sabyr.
Suddenly, a green beam is shot from the sky, bisecting the Grimm that tried to attack Blake. More beams are shot at the remaining Grimm trying to charge at the group as someone flies above them.
These beams are revealed to be made by the recreated Penny Polendina, who lands after all the threats are gone. Pietro approaches the group to reintroduce her.
Team RWBY, Jaune, Nora, Ren, Qrow and Oscar prepare to return to Pietro's house to get more answers. However, they are then bound and arrested by the Ace Operatives for stealing an airship and unauthorised weapon usage and have their weapons and the Relic of Knowledge confiscated. Their leader, Clover Ebi, assures that they can talk out this situation up at Atlas before loading the group in the back of an aircraft.