This riddle is a bit more difficult but it is given by Yeshua and He is speaking to Peter. Yeshua says:
“And I also say to you that you are Peter, and on this rock I will build My church, and the שער of שאול shall not prevail against it.” – Mat 16:18
Good luck with this one! If you figured out the others you should also get this one but I will give you a hint. שער doesn’t always mean “gate”. Also, take into account who Yeshua is speaking to. That’s important.