RECAP:
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Malachor

"It was nothing more than a slaughter. A slaughter caused by one of my creations. Blame lies with me, for creating it. The situation forced your hand, anger forced mine. You realized that unless action was taken, the fleet would be destroyed, and the Republic would fall. None of us realized the magnitude of what we unleashed."

— Bao Dur to the Jedi Exile Meetra Surik

Jaune dreams of Nihilus's last moments as a Jedi during the Battle of Malachor V. He later wakes up in the hospital and is questioned as to how he knew what to call the terentatek.

Tropes in this chapter include:

Another Man's Terror: While viewing Nihilus's memories of the mass shadow generator being deployed during the Battle of Malachor V, Jaune believes he's witnessing Nihilus's death. Subverted given that Nihilus didn't die, although he might as well have been.
Asleep for Days: Upon waking up in the hospital, Jaune learns that he was asleep for three days while recovering from his wounds.
Can't Spit It Out: Jaune finds himself unable to tell Ozpin about the Mask of Nihilus due to Nihilus's spirit mentally compelling him not to.
The Cloudcuckoolander Was Right: Nora pretty much nails it on the head with her theory that the memories Jaune has take place "a long, long time ago, on a planet far, far away, with aliens and technology beyond anything [they] have". Of course, all her teammates think she's crazy.
Cruel and Unusual Death: In the flashback, Nihilus kills one Mandalorian by lifting him up in the air before imploding their body with his telekinesis.
Dramatic Irony: Jaune dismisses Nora's theory about aliens because he misidentifies two alien species he saw during his dreams as Faunus.
Ear Ache: During the Battle of Malachor V, Nihilus unleashes a Force Scream so loud that the Mandalorians surrounding him start to heavily bleed from their ears, implying that the scream burst their eardrums.
Fanservice Extra: The nurse who cares for Jaune after he's hospitalized by the terentatek. She's a Hospital Hottie who wears "a skirt a bit too high" and her shirt shows cleavage. She also subjects Jaune to Marshmallow Hell when she leans over his hospital bed to adjust his pillow and unknowingly smothers Jaune's face with her bosom.
Final Solution: By the time of the Battle of Malachor V, Nihilus's hatred of the Mandalorians has fully enveloped him to the point where he sees them all as nothing more than savage barbarians and he vows to personally see to it that the Mandalorians are "erased from existence", implying that he planned to genocide the entire Mandalorian race once the Mandalorian Wars were over.
Ghost Memory: Jaune has received Nihilus's memories, explaining how he knew what the terentatek was but doesn't know how he came by this information.
Marshmallow Hell: Jaune is briefly subjected to this by the nurse when he wakes up in the hospital.
Reasonable Authority Figure: When Jaune insists that he doesn't know anything else about the terentatek and keeps asking to see his friends, rather than continue to push him, Ozpin relents and stops questioning him.
Suddenly Shouting: When Ozpin and Glynda keep asking Jaune how he knew the creature they fought in Forever Fall was called a terentatek, Jaune abruptly loses his temper and shouts that he doesn't know.
Suicide Attack: During the Battle of Malachor V, one Mandalorian who was wounded by a lightsaber decides to sacrifice themself by leaping at the Republic's soldiers after activating a grenade in their hand.
Tears of Joy: Pyrrha, Nora, and Ren all shed tears of happiness while hugging Jaune after seeing that he's alive.
Time Skip: Jaune wakes up three days after the events of the previous chapter.
Title Drop: The narration near the end of Jaune's dream sequence.
He felt the death, he felt the pain, he felt the lesson of Malachor.
A Truce While We Gawk: When the Mass Shadow Generator is activated during the Battle of Malachor V, the Revanchists and Mandalorians halt their battle and collectively stare in horror as a black hole suddenly appears above the battlefield and starts sucking everything in.
Unrealistic Black Hole: The singularity created by the mass shadow generator in the flashback counts. Obviously real-life black holes don't shoot out green lightning.
Yellow Lightning, Blue Lightning: The black hole created by the mass shadow generator shoots out bolts of green lightning which char the surface of Malachor in the flashback showing Nihilus's transformation.