Ten to fifteen paintbrushes are required for this trick. They can be found anywhere in the game, particularly in boxes, shelves, etc. You can use this glitch even if you have yet to start the main quest yet. Once you obtain all the paintbrushes, go in front of the Temple Of The One in the Imperial City Temple District. Climb you way to the top using the "Floating paintbrushes" glitch. Once you are close to the top, jump on the roof. You will go through, landing inside The Temple Of The One. You can see everyone else but they cannot see you. Walk close to where the door would be if you were inside it normally. You will see the top half of the same door you are in front of. Select it to enter the real interior of The Temple Of The One. Notice the hole in the ceiling where the light comes down. You will see a red sky. Walk outside and and two Oblivion Gates will be opened. Your quest will be updated, indicating that Dagon is here and that you should speak to Martin. Even if you are not close to completing the main quest this glitch will still work. Go inside both of the Oblivion Gates and get the Sigil Stones. Later you will end up crossing over Dagon. Kill him then talk to Martin in the Cloud Ruler temple.