Percy moving in a time freeze

Kronos roared in outrage. "Luke Castellan is dead! His body will bum away as I assume my true form!"
I tried to move, but my body was frozen again. How could Annabeth, battered and half dead with exhaustion, have the strength to fight a Titan like Kronos?
Kronos pushed against her, trying to dislodge his blade, but she held him in check, her arms trembling as he forced his sword down toward her neck.
"Your mother," Annabeth grunted. "She saw your fate."
"Service to Kronos!" the Titan roared. "This is my fate."
"No!" Annabeth insisted. Her eyes were tearing up, but I didn't know if it was from sadness or pain. "That's not the end, Luke. The prophecy: she saw what you would do. It applies to you!"
"I will crush you, child!" Kronos bellowed.
"You won't," Annabeth said. "You promised. You're holding Kronos back even now."
"LIES!" Kronos pushed again, and this time Annabeth lost her balance. With his free hand, Kronos struck her face, and she slid backward.
I summoned all my will. I managed to rise, but it was like holding the weight of the sky again.
Kronos loomed over Annabeth, his sword raised.
Blood trickled from the comer of her mouth. She croaked, "Family, Luke. You promised."
I took a painful step forward. Grover was back on his feet, over by the throne of Hera, but he seemed to be struggling to move as well. Before either of us could get anywhere close to Annabeth, Kronos staggered.

He stared at the knife in Annabeth's hand, the blood on her face. "Promise. "
Then he gasped like he couldn't get air. "Annabeth ..." But it wasn't the Titan's voice. It was Luke's. He stumbled forward like he couldn't control his own body. "You're bleeding. . . ."
"My knife." Annabeth tried to raise her dagger, but it clattered out of her hand. Her arm was bent at a funny angle. She looked at me, imploring, "Percy, please ..."
I could move again.
I surged forward and scooped up her knife. I knocked Backbiter out of Luke's hand, and it spun into the hearth. Luke hardly paid me any attention. He stepped toward Annabeth, but I put myself between him and her.

TLO ch.19