If the Cardinal wanted hi dead, he could have attacked him the moment they entered the Northern Continent. However, the Cardinal's actions suggested otherwise.
Eren understood that the Cardinal's plan was not as simple as just killing him. The reason he brought Eren here and allowed him to witness the gruesome ending of the Demon Sect members was for a single purpose.
The Cardinal wanted Eren to feel hatred towards the Northerners. The Elders of the Demon Sect were known for taking revenge, even for the slightest of grievances.
The Cardinal expected Eren to go berserk and attack the Major Families of the Demon Sect that ruled over this area, ultimately leading to his death at the hands of the Necromancer Tower.
This way, the Cardinal could establish an undeniable grudge between the Necromancer Tower and the Demon Sect.
It was truly unexpected for Eren to simply suggest returning without seeking any revenge. Was he really the same person who had destroyed multiple sects because a Sect Master offended a random disciple of the sect?
When Eren suggested returning, he momentarily lost his composure. To stop Eren, he outright suggested what he wanted Eren to do, telling him that there was hope of saving the envoys who might still be alive in captivity.
"Even if they are alive, they could have been taken to the Necromancer Tower. It will be foolish to attack the Necromancer Tower alone," Eren told the Cardinal, enjoying the panicked look on his face.
He climbed on the Pegasus, implying that he was already prepared to leave.
"T-that is not true. It is most likely that the Major Family that controls this area is keeping the envoys," Treniel said, placing his hand on Eren's Pegasus to stop it from flying.
"How do you know that the Necromancer Tower doesn't have them?"
"I-i have some spies working for the Kiel family that rule this area." The Cardinal made up a story. "The spies informed me just this morning that the family is holding some hostages, waiting for the Necromancer Tower to send a representative to take them back."
Eren made it clear to the Cardinal that he was somewhat conflicted about accepting this suggestion.
It was only after taking his sweet time, he agreed, "In that case, I will accept your suggestion. We are taking down the Kiel Family."
The Cardinal felt extremely happy in his heart, even though his expressions remained just as calm. His plan had almost failed, but eventually, he succeeded.
He released Eren's Pegasus and walked over to his Pegasus. He sat on his Pegasus which started rising in the air, advancing towards the Kiel Family.
....
Inside the Kiel Family, the Patriarch was sitting on his knees. Meanwhile, Fey was sitting on the Family Head's Seat.
"Did you find the girl?" Fey asked the Kiel Family Head, who meekly shook his head.
"Useless! You couldn't even control your own daughter? How dare you let her run away instead of sending her to my bedroom like I asked?!" His tone grew angrier as he kept scolding the Family Head.
"I have instructed people to search for her," the Family Head answered, unable to control his own actions. Even though he had his consciousness, his body was truly treating Fey like his lord.
"Find her. I want to teach her a lesson for making me wait! If you fail to find her, I might as well have you destroy this useless family with your own hands."
The Family Head nodded.
Fey then changed the subject. "Also, how long until the other Family Heads arrive?"
"By tonight, the leaders of all major families in the Northern Continent should be here," the Family Head replied.