Since he had an extremely important thing to ask Jace, he had to take Jace away and make him talk.
For as long as Lucas could remember, he had never heard his mother mention anything about her family, and Lucas didn't know much about her. Now, Jace actually said that he knew something about his mother. So regardless of what the secret was and whether or not Jace just made it up to save his life, Lucas had to get to the bottom of things.
If this white-bearded old man continued to stop him, he didn't mind fighting him to the death!
The old man's chest heaved up and down vigorously. Clearly, he was enraged by what Lucas said.
But he had been entrusted by someone to protect Jace, so he couldn't let Jace fall into Lucas's hands and die.
"Lucas, are you sure you want to become my enemy?
"I admit that you are indeed a very strong opponent. In fact, you're the strongest of the younger generation I've met. Even I may not be a match for you.