Loki's actions put the swordsman in a corner. He became desperate, so he said to Loki, "You have to give me a way out, or I will not let you gain anything."
In response, Loki smiled and said, "What do you suggest?"
He replied and asked a reasonable question as if he was seriously considering the offer. But he didn't stop rushing towards the core of the world at all.
In fact, he seemed to have become faster. So not only did he not stop to negotiate, but he appeared to want to reach the core of the Cave Heaven much earlier than expected.
The swordsman saw this and said, "Stop, and I'll give you half of my Cave Heaven."
Loki nodded and said, "That sounds good. But I also want one of your Divine Metacs."
This was literally asking for half of his life, as losing one Divine Metac meant that he would lose half of his strength. When the loss of half of his world is also factored in, he will only have 25% of his strength left.
