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.
The same way you got your first key. ( If it's "Elemental Workshop" Quest )
sorry you cant make keys on runescape unless of corse it is the crystsal key.
There isn't a key for it unfortunately.
A brass key.
The first player in Runescape is my vagina and penis.
Buy it, get it from the Hill giants.
You kill chaos Dwarves there I think, and they drop the key.
open the dragon chest in Taverley
It is used to open the muddy chest
You can buy soft clay on ge, and you can buy a key mold.
Talk to the banker NPC in-game about your key, should give you the option.
Runescape is currently owned by Jagex Ltd. The first beta version of Runescape called Deviousmud was formed in 1997 by Andrew Gower. The first actual MMORPG was Runescape classic formed in 2001. Runescape classic changed to Runescape 2 on March 17, 2004. Runescape 3 (known as Runescape HD) was made in 2008.