Predecessor Builds > Aurora > Tank Aurora Support

Item Order: adapt to enemy team as with any tank build. Fireblossom against phys. damage (almost always as support), Flux against magic damage.
Build Unbroken against heavy cc or cc coupled to burst. Tainted Guard for Anti-heal, but a lot of smart enemies will hit your squishy allies rather than you in which case it will be useless, so only build it situationally.
Crest: Titan or Guardian. Guardian is better in terms of gold, but if you have an inter on your team (as you usually will), the cs restriction greatly limits your ability to fill that gap. Furthermore, in many cases of late game you will need razorback to retain your viability. Tempest is also good if youre Offlane (and decent in Jungle), but then you're in the wrong build here. Dont take it supp, as the stacks come mainly from CS and you dont get that as support.
Ability order: E lvl 1, Q lvl 2 for engage or RMB if you dont have trouble engaging (e.g. against a melee supp who keeps fisting you). Lvl 3 whatever's left of your basic abilities. As always, max RMB, followed by E and Q last. (level R whenever possible, goes without saying)
Playstyle: Try to be aggressive lvl 1 - 3. You can usually get at least one of the enemy duolaners very low early, setting you up to a good lane. If you fail to get a good trade early, early levels can be rough at times as you may keep getting poked. Remember to look for roams once you have Q and the opportunity to roam. Mid and Offlane can benefit a lot from receiving good early ganks.