Aurelion Sol was largely forgotten about by Riot Games after his rework. He has fallen into obscurity with a 1% pick-rate and a <1% ban rate. However, after many games with this character and role, I've discovered it works quite well. To be very clear, this information won't help you much if you haven't already played Aurelion Sol; There are other guides that go more in-depth on who he is for new players. This is for those players who've already played him and/or know how he works.

Aurelion Sol support is an aggressiveness amplifier, meaning the optimal playstyle is to be an aggressive poker who sits in bush most of the time and provides plenty of opportunity for your bot laner to attack. Make sure you learn Celestial Expansion first thing, though you don't have to use it before level two unless an engagement occurs. Try to be in bushes around the time level 2 hits. Once it does, level your Q, Starsurge. The idea is to sit around/in bush and throw out the QW combo whenever the an opportunity reveals itself. If the support happens to occupy bushes, use your Q in combo with your bot laner to make them regret it; Your Q will cover an entire bush easily. It is important to upkeep your wards in those bushes so you can keep tabs on where the enemy support is. The QW combo will drain your mana very quickly before the first couple backs. However, ensure you do not back before level 3 unless absolutely necessary.

Synergy is very important with this character. Tristana and Miss Fortune are the two best synergies I've had so far. With an aggressive character such as them, you can use your QW combo in combination with your bot laner to either burn the enemy down significantly or kill them if possible. You will almost always be within Ignite's range after QW, so don't be afraid to use it with a basic attack or two to get that final bit of health off. Hopefully, you will have level 3+ by the first back. If you do, you'll have your E, Comet of Legend, to get back into lane quickly. Any time you have your E as you are coming back to lane, use it in combination with Starsurge to get a big star into lane. Even if there is no one visible in lane, you will still at least hit minions or any bushed players. If they aren't pushing on tower or you simply don't see them, it's generally best to aim this combo in the middle of the lane, into the enemy-side bush.

The objective here is to shove far enough into tower that you can get some structure hits alongside your minions or, depending on the team comps, attack them under their tower. If for some reason you can't do this, either because they're team comp is too good or their jungle is camping, just play on your side of the river opening and look for opportunities to stun for your bot laner.

Once tower is gone, your objective will be to assist wherever you are needed. If you can't figure out where that is, follow your bot laner and/or support mid. Aurelion Sol is not a dueler; His fighting style is to provide stun; burn down enemies' health; catch low-health enemies with his R, and have the ability to fly anywhere on the map he is needed quickly. Assist in team fights to feed up your teammates with takedowns. Unless your team needs to defend or take a neutral objective, your best bet towards late game would be to split push bot or top lane, whichever is farthest away from the majority of enemies on their team. Aurelion Sol's E Comet of Legend is, hands-down, the best limited gap closer in the game (balanced out by it's very high cooldown). I cannot tell you how many games I've won by running it down a lane while my team fights in mid, and then, by the time an enemy makes their way over, I use Comet of Legend to fly back towards the base to escape punishment. Doing this only a few times while your team fights can change a lane diff into a lane collapse within a few minutes. Don't worry about not being with your team in a fight. Unless it's over a late game neutral objective, such as Baron or Elder, the massive lane damage will largely make up for it.

The mid/late game strategy is a matter of figuring out what's best for your team. Fighting with them/defending, or splitting to a lane to chunk it's tower down with the intent of E'ing out without punishment. This strategy has gotten me to Mastery 7 on Aurelion Sol with (as of writing this guide) over 102,000 points on him.

I sincerely hope that this guide fuels some players to try this out for themselves. This is the first guide I've ever made, so give it a vote if you found it helpful or intriguing. Aurelion Sol is an amazing character with some of the best lore design I've ever seen. I just hope Riot doesn't completely forget about him.