Kapitel 606: The call of the cosmic jewels

The next set of memories contained 12 sizable fragments turning into Shadow Beings with a spell in an alien language, each one eventually infecting a human and turning them into dark creatures.

Surprisingly, one of the dark creatures created by this Shadow Being was captured by the military and brought to the Star Labs. Azzy saw Eren's dad there with the other scientists as they experimented on the unconscious dark creature.

Louis wasn't seen anywhere though.

The unconscious creature then got up and went on a rampage, killing some and infecting some. The ones that were killed stayed dead but the ones bit by the creature became zombies. 

Another memory showed a bunch of soldiers killing a dark creature somewhere, reducing the zombies into dead bodies.