Just as Eren was about to begin the crucial part of his plan, something favorable happened.
Eliza decided to end Demonmir's life once and for all, even though she knew that he had been used as a pawn by Eren to distract her.
Demonmir had tried to kill Eliza due to being influenced by the Life and Death Altar, and she had taken it personally.
With renewed ferocity, Demonmir and the Witch of the Enderflames started battling each other. They sensed that Eren was up to something using their Soul Senses and had felt the mana fluctuations released by Reen's Soul Seed as well.
However, they didn't have enough time or window of opportunity to keep track of his doings.
It looked like Eliza was bound to outlast Demonmir and win by default. She had also started using the other Sin Series Marks on him now that the injury on her soul had been healed to some extent.
