well Zhonya's Ring is now Rabadon's Deathcap but i have played around with less Archangel's staffs and more Rabadon's Deathcap but this is the most powerful AP build I can figure out. I will hit a little under 1200 at level 18 with this build but with the Elixir of Brilliance you will hit over 1200. I like cool down runes cause I can now finish my Soul Shackle and have my dark binding and tormented soil ready for another shot if that didn't kills them. The down side to this build is not much defense or life but with your black shield you can make up for that loss with all that AP.