The essence of this build is Tank mythic > 2 AP items (second one always being Cosmic Drive) > Tank legendaries. So i was inspired by xPetu to try out Cosmic Drive on shen because i've always found AP to be very strong by ults turning a whole fight around but on support building AP mythics will be expensive and make you more vulnerable than going Tank, so xPetu's Cosmic theory mixing tank items with 2 strong AP items was perfect. Because i've mostly been playing Shen support since i enjoy it a lot more i started theory crafting this Cosmic Shen build for supports and realized as supports we can utilize the support starter item which will upgrade your AP for you over time, this means you are not forced to go Banshee's over Zhonya's and you don't have to take an AP stat rune which is definitely worse than the ability haste stat rune. With maxed out Relic Shield, Zhonya's and Cosmic you have precisely 160 AP total which is exactly what you need to turn Cosmic's passive on. So this idea is very work in progress and while im writing this i'm still testing it out but i wanted to get the idea out there so i might get some more opinions on it.