How do you get the first key on runescape?

Answer 1

In future can you please give us more detail on what your after, there is more than one key in Runescape, thankyou.

My Guess:

You are doing the "Demon Slayer" quest, if I'm right to find the first key go to the northwest corner of the castle to find a set of stairs. Climb them twice to reach a room with Captain Rovin. Speak to him and tell him that a demon is going to invade the city, that you have to defeat it, and you need his Silverlight key. Select the option that says "Sir Prysin said you would give me the key" and then select the option that says "Then why did he give you the key?" After bringing up Sir Prysin's clumsiness he will hand it to you.

Answer 2

Go to the Pheonix gang hideout and ask to join. Then he will tell u to go to the bar and kill a man named jonny the beard and give them his papers then they will give u the key.