Lucius didn't think that the idiom was something used in this world, but back in his old world, it was said to warn against someone waking up a matter that they were unprepared to deal with.
The Black Rose Knight was afforded certain privileges because of his station and relation to the King of Grantz, but if the man tested Lucius's nerves too much, then he wasn't completely safe.
An unfortunate accident coming across this Black Rose Knight would be something he might encounter.
Luckily for the Black Rose Knight, Count Gabriel Inanis descended down from the staircase bearing the authority and air befitting of his status.
"Gentlemen, my son has only returned from the safe house and though I appreciate all of you checking on his condition, it is also important that he be given some time to catch his breath and relax. Save your questions for later."