I want to know the answer to the following question:
What is the only known gateway between Twilight Realm & Hyrule?
All the background I'm provided with is that "Now able to use it to switch between both forms at will, Link is led by Midna to the Mirror of Twilight located deep within the Gerudo Desert, the only known gateway between the Twilight Realm and Hyrule.". Is that enough to answer the question?
Answer: yes