Riot Games has announced server maintenance in order to deploy League of Legends patch 8.3 and if you don't feel like reading the wall of text on their main page, here is a more coherent alternative.
Riot is being tentative with balance changes in this cycle and some of the most meta influencing champions and runes are being changed but only ever so slightly.
The Inspiration rune tree is getting the most changes, as expected. Stopwatch craze is bound to continue as the rune didn't get nerfed at all. It was however moved to the same tier as Magical Footwear so if you opt out for the get out of jail free card, you will no longer get free boots with it.
You will still have Future's Market in the second tier that will let you compensate for the loss of the free boots, as being able to get loans to catch up with opponent's items or gain an upper hand in lane will eventually pay off. Unsealed Spellbook is still there, but the CDR on summoner spells is now 15 per cent down from 25. It will remain relevant in the meta.
The moment has come - creepy birdguy Swain is getting a full VGU treatment. Certain indications about widespread Harry Potter fandom at Riot Games were already present, such as Rabadon's Deathcap bearing many similarities to the sorting hat, but this change might be the one that will bring J.K. Rowling to their doorstep, lawsuit in hand.
Aside from visual update, his gameplay is also largely altered. He may prove to be broken, as the current scaling and base damage of his abilities is rather high. Swain's Q ability acts like a magic shotgun blast that will deal up to 348 + 0.96AP at max rank. With 700AP you will be able to slash an enemy carry's health in half assuming you bought Liandry's Torment, Sorcerer's Shoes and Void Staff for maximum spell penetration. Consider running him when your jungler picks Ivern as his root will let you knock your enemy towards you and move you point blank for a maximum damage blast, all with one right click. This ability essentially lets him burst squishies on top of being a super mage tank.
Swain's W , Vision of Empire (Rito grammar) - is an ability that is somewhat hard to land, with a similar skill shot mechanic to his old W, Nevermove. It is considerably easier though with the new Nevermove which was moved to E, as it will root the enemy in place for 1.5 seconds even on rank 1.
The great thing about Vision of Empire is that it reveals invisible units for 4/5/6/7/8 seconds, depending on the rank. If you had trouble with countering the likes of Akali, Vayne or Kha'zix simply because you couldn't click on them due to their stealth abilities then this spell is the answer to your prayers. Land a quick E-W combo and just burst them with your Q as they remain unable to go invisible and run away from you. It is worth nothing that Nevermove now behaves like Ahri's Orb of Deception and is easier to land than before, but the ability only roots the first champion it hits on its way back to you.
Swain's R now gives him a flat amount of additional health in addition to draining surrounding enemies' HP, limited to a maximum of 3 enemy champions. After draining 150/300/450 HP you gain the ability to cast Demonflare that will end his transformation and deal splash damage to all enemies around him. The damage will depend on the number of Soul Fragments previously collected from Swain's passive and W. Scaling is fairly high and Swain might just prove to be similar to Vladimir - a tanky mage with high sustained damage. Their differences are reflected in Swain's regenerative powers being limited to his R that now has 120s cooldown but the burst and crowd control potential is higher than Vlad's and the right conditions for deleting squishies will be met more often.
For the exact numbers on his abilities you can consult LoL wiki , that has already updated his info.
Naturally, the massive update on the champion rework didn't stop Riot from working on regular champion balance, but it remains to be seen if the balance changes will have the desired effect.
Azir got hit by the nerf bat, and his early game power is going to suffer as a result of higher cooldown on his Q. Jhin is getting some love as he disappeared from meta in favour of hyper carries. He was still viable but the damage buff to his ulti is an attempt to bring him up to par with the meta carries.
Katarina's damage from picking up daggers was reduced but she will still one shot you, so keep either banning or picking her. Same goes for Zoe. I hate Zoe with all of my heart but it appears Riot doesn't. Her power barely got dented, as she will now be able to one shot you only once every 8.5/8/7.5/7/6.5 seconds. It's a 1s change on the first rank and 0.25s on max rank.
Surprisingly, the top lane dominators Vladimir and Urgot didn't get touched in this patch which adds them to the ban/pick list. There was a big list of changes/reverts planned for Rengar but all of it got postponed for a later patch. Until then the carries will have to deal with his current state. Best protection against this catman was always a good support, make sure you get one.