Break Down In Negotiations.

The demon god knew that Marlinto was probably going to die when Ragnarok showed up in his territory. But it didn't warn the Primogenitor or tell him to escape. It is all to acquire more information about Ragnarok. 

It is not angry about Ragnarok's rejection even though it risked Marlinto's life for information because it is confident of victory. It is a confidence brought about by grasping the whole situation in its hands. After all, it literally has the whole plane in its grasp. 

Ragnarok continued, "I have no intention of enlightening you. This meeting is not for that. You know what I want." 

"Yes. I know that. You want to leave this dying plane. You also want me to swear that I won't come after you. I thought Marlinto gave you my answer to that question."

"That was before. Now I am about to kill one of your Primogenitors and can kill more if you refuse me. What is your answer now?" Ragnarok asked.