First click the one that says "Click me to become a vampire!" then click the second "full vampire" stone. + There are two similar tombstones in the room. + Type coc testvampireinterior to be transported to the developer's vampirism testing area. O If you want to become a vampire after taking the cure vampirism potion, it is possible using console commands.
Instead of entering 25, you can enter 1, and your player character will be at 25%. Theoretically, you could become a higher-up vampire by typing in 50 or 75 instead of 25 in the command, but this does not appear to work. O This will automatically turn you into a 50% vampire, however, you will not be able to advance in vampirism or go back to 25% vampirism, and you will lack the Hunter's Sight ability as well. Thereafter you will be able to become a vampire through any of the normal means within the game. O In order to become a vampire again through being infected with Porphyric Hemophilia simply type the following into the console, Set PCVampire to 0 and Set vampire.hasdisease to 0.