Eren let Eliza settle her score.
As a result, the Anfang Alliance had a consistent headache for the past nine months.
Eliza could even fight and win against Sages while still being a Grandmaster Ranker. She specifically targeted the Sages from the Alliance, killing many of them during the last nine months.
Thanks to her acceptance of another soul that was Lady Zee, the behavioral restrictions Eliza had on herself due to her Sin Series Ability weren't as limiting anymore. One could say that her always-active Sin Series Ability had evolved to better accommodate another soul. She wasn't as pressed to keep her pride unsullied as she was before.
As such, Eliza could run away from the Anfang Alliance when things became difficult for her to handle. And nobody could stop her if she decided to retreat from the battles of her choosing.
Eliza's vengeance was one of the reasons why Sage Zavir was so keen to strike a deal with Eren. He knew that Eren had subdued Eliza and could control her actions to a larger extent.
As such, one of Zavir's conditions for striking business deals with him was to make Eliza stop her rampant attacks on the Sages who had nothing to do with what had happened in the Calamity Era. Eren agreed readily because he had other plans for Eliza as well.
After much contemplation, Eren had finally settled on which world to visit right after leaving Anfang. He was about to take Eliza, Layla, and Leela with him, taking them to Labh Salem.
The butcher's plan was simple. He was going to use witches to counter the witches of Labh Salem. Of course, he didn't know what kinds of surprises awaited him in a foreign world. However, he always liked to prepare in advance.
Just like how Eliza had used Eren to achieve her own goals, Eren had something similar in mind. House Samael's roots were in Labh Salem and he could use that to his advantage after leaving Anfang.
Eliza had agreed to help Eren get his hands on an Elder Seed Artifact that was in Labh Salem. This was something she needed to do to make herself not feel indebted to Eren's generosity in sparing her life.
There was more than one reason Eliza was compelled to follow Eren. After wreaking havoc all across Anfang during the last nine months, she felt that her vengeance wasn't as satisfactory as she wanted it to be. This was because those who had wronged her and all the other half-bloods had already left Anfang a long time ago.
Assuming things went well for these aggressors, they would still be alive and prospering in foreign worlds. After all, they were Sages from Anfang during the Calamity Era. As such, they had a better chance of survival even in foreign worlds.
Eliza wanted to target these Rankers who had exceeded the standards in Anfang. She wanted to destroy them for what they had done to her.
Of course, Eliza wasn't delusional enough to think that she could destroy these Rankers with her current Ranking Status. However, identifying the targets was her priority at this point. She could set her goals and work hard in Labh Salem to match the advancements her enemies had made before destroying them completely.
Furthermore, Eliza also wanted to see what remained of her House in Labh Salem after all these years. She knew that House Samael had been persecuted in its home world due to various circumstances. These circumstances were the reason House Samael was forced to seek shelter elsewhere.
Eliza wanted to break her bloodline shackles. And the connections she shared with the original family from Labh Salem could help her in her endeavor as well.
The Witch of the Enderflames had no interest in the Elder Seed Artifact that Eren wanted for himself. Being from Anfang, she did not even know or understand about the Elder Seed Artifacts as well. As such, she agreed to help Eren get the artifact without much contemplation.
Eren and Eliza both knew that they couldn't just delete the history they had between them. They couldn't just shake hands with each other to explore Labh Salem, which had become their common destination.
However, for better or worse, they both knew how to prioritize their self-interests. As such, their temporary alliance did not see many hiccups in formation. It also helped that their self-interests did not intersect with each other.
Eren was fine with Eliza attracting the attention of the big leagues. He was fine with her seeking her due vengeance as long as it did not hurt his interests. Lastly, he was fine with her reestablishing her ties with her familiar roots. If anything, he wanted to see if he could ally with House Samael from Labh Salem as well.
He could use the draconic half-bloods as a launchpad to instantly gain a foothold in a foreign world. This was provided they held some importance related to the artifact he was seeking in Labh Salem.
Eren could have let Lady Zee's consciousness win its fight against Eliza, making her the dominant soul in their soul fusion. It would have allowed Lady Zee to suppress the Witch of the Enderflames, enabling her to gain control of her body.
However, after much thinking, Eren decided not to do that. This was because doing so would have made Lady Zee or Eliza less useful.
Eren had to say that Eliza was a better Ranker than Lady Zee and she knew how to use her gifts well. Only Eliza could make use of her Sin-series Abilities effectively. Only she could summon the Enderflames and black flames both.
As a powerhouse from the Calamity Era, the Witch of the Enderflames could dominate the talents born outside Anfang as well, making her come across as a much better choice as a pawn in Eren's eyes.
If Eren were to help Lady Zee suppress Eliza, all of Eliza's advantages as a powerhouse would also get suppressed. This was why he discarded the idea.
A strong pawn was a bit hard to control but it was useful in the hands of a right manipulator. However, one could not make much use of a weak pawn even if the latter were to remain loyal to their masters.
