He knew that he would be facing an angry crowd, but he entered the 'lion's den' without hesitating.
the club's reputation as a 'den of iniquity' [=a place where immoral or illegal things are done]
He spent most evenings in the 'den' reading and smoking his pipe.
(..) A hero! A hero! I knew that the sea would bring us a hero! So, will you go up to the moors, to dark pool by the cave and kill the monster in its den? I have fourteen brave Thanes with me. We have been long at sea. It is high time, mighty Hrothgar, to break open your golden mead, (..)2007 Beowulf