Authority Over Time: The Frozen Flow.
Alephee wielded her powers and the time flow around her was almost stopped. A domain was created, taking her, Eren, and Sara inside. This was her domain.
Eren felt like he was submerged in some thick and illusory liquid that prevented him from moving freely. Even his heartbeat stopped. His thoughts were also affected by being inside the Frozen Flow.
This was an exclusive time-element barrier or domain that nobody could enter or leave willingly without Alephee's permission. The concept of time in the domain was slowed down as Alephee wanted it to be. Even Eren and Sara could only keep their minds working for them inside the barrier, if only barely. They lost their ability to move even an inch of their bodies.
Eren had experienced this power before. Alephee used this power for the first time after Eren tamed his spirit beast. At that time, Alephee struggled to keep this power active for a long time because her vessel wasn't strong enough