1) Beard the lion in his den. 

2) If you don’t enter a tiger’s den, you can’t get his cubs. 

3) Father retreated to his den.

4) The snakes den up during the winter.

5) There is a big fox den on the back hill.

6) He finds himself in a den of ruffians.

7) He would often retire to his den.

8) Tom bearded the lion in its den.

9) They made themselves a den in the woods.

10) The kids are watching television in the den.

11) The old woman wanted to den up.

12) Den suffered terribly from stage fright .

13) He thought of New York as a den of iniquity.

14) Den left the next day, needing to make a clean break .

15) Den had dug a deep hole in the centre of the garden.

16) Her mother was convinced that London was a den of iniquity.

17) Den he start ta eat kids?

18) The school's boiler room was a den of mine.

19) The wood-panelled den looked dark and forbidding.

20) They could become a den for juvenile delinquents.

21) I enter the sci-fi disco den.

22) The mountain Nui Ba Den was a singular feature in my area of operation and a good example of hazardous terrain.

23) The den was on the first floor at the rear of the house[sentencedict.com], with windows overlooking the garden.

24) Gran's been on the sauce again - she's passed out in the den.

25) He could hang loose when he went into the den of vice.

26) The bandits fled in disorder when they heard that a regiment of soldiers were maching to their den.

27) Joyce explained to Paul in a very loud voice that her den was this way.

28) Towards the end of her confinement she climbed up into the den and refused to leave.

29) They hoped for a home theater and a showcase kitchen blending seamlessly into their den.

30) I haven't found out yet what they got up to in their opium den with Coleridge and de Quincey.