Heyo my name is K4T4N4, peaked platinum these two splits and im trying to go for diamond playing mainly Sett (yes i play Sett top, mid and sup). I started playing Sett a lot this year and the first thing that came to my mind was, how im supposed to learn what does every champion and how to win against them? Like in spirit blossom Sett lore, he travels far and wide in the spirit realm challenging foes while looking for his father. We can relate to him, having more than 150 different champions to deal with trying to go as far as our skills allows us to peak. This is what pushed me to make this record of every champion i have faced with Sett so far so new Sett mains can have a better idea of what to do. I have the intention to keep filling this guide as i keep fighting new foes in my way to higher ranks and actualize it the more i climb and the more i experience.

Sett is a powerhouse in early game, tanky while still deals massive damage who can easily turn a 1v2 to his favor and has a reliable engage into the enemy backlane. His pasive allows him to regen hp when he is low making hard to poke out of lane and his design and playstyle are pure testosterone. Sounds pretty good right? but not everything is color pink. First of all if you dont know how to properly kite you wont get his full potential, he has long cds and after you use your W you lose a lot of presure, also has one if not the slowest basic movement speed in the game making easy to kite and hard for him to engage and stick to enemies with dashes. He is also very obvious about what he intends, charge grit, W and deal true damage, try and R the enemy with the highest hp pool, etc.
On the good side his teamfight potential is huge and can turn the tables in one if played correctly, always useful in 5v5 situations.

If you have the time look and read what everyone of his skills do, but in general, Sett´s passive gives him hp regen per hp lost and his second auto attack has slightly more range and deals more damage, useful for poke someone when they try to farm.
His Q empowers his 2 next auto atacks, deals hp percent that scales of AD and gives you a little bit of extra MS towards enemies. It resets auto attack animation but its ideal to Auto-Auto-Q-Auto-Auto to maximize dps.
His W deals true damage in the center and ad in the sides, the damage calculates on how much grit you have (in english, how much damage have you stored, Sett glows when you have stored a lot) and scales of AD and HP. You can Flash in the middle of your W and i highly recommend to master this mechanical reaction, it had gave me more kills than i can count.
E pulls enemies towards you in a rectangular area, you can extend the reach if you hit it diagonally with the corners, it slows a little and if you hit a target from both sides they will be stunned for a second.
R serves as an engage tool and as an escape, if you get ganked from behind you can ult towards safety. It suppreses enemies meaning that they can only get away with stuff like QSS or GP orange and it interrupt skills like Samira´s R. There is no much to be said, you can insec someone with E stun, Q movement speed to get behind them and R towards your team, and slows everyone in range for 99% ms so it basically immobilize them. The shockwave damage escales of the one you ulted extra HP.

In most matchups, early you will look for a kill if possible, Sett´s 1v1 potential in the first 3 levels is huge, farm and punish with your second auto if the other laner walks up to farm, if he miss steps E stun him and try to force him to trade or run. If you get prio in lane help with scuttle contest, it can lead to a double kill sometimes! If you get first blood, shove and recall to spend gold, if you shove but dont get a kill, and your jungler wont contest that scuttle, go back for a cheater recall and buy boots.
In those rare scenarios where you will get harassed in early, just farm and try to priorize meele and cannon creeps, let the wave push towards you and politely ask your jungler if it would be possible a gank.
You will get a power spike after stride breaker or ruined king, keep that in mind.
After plates fall keep trying to take down top if you havent already and be aware of timers, after the second drake you should start to group with your team to contest the 3rd drake or, in lower elos, in case a teamfight starts in mid.
In teamfights you should learn to read the situation, if your win condition is to make the 9 0 vayne kill everyone, try and use your R to peel, if the win condition is to pick up the 9 0 enemy vayne, R into the backlane and see if you can catch her so your team burst her down.
Finally in longer games, your chances to carry decreases with every extra minute to the point where it will not depend on you anymore, sure you can engage and be useful but this is where hyper carries begin to shine and if your team isnt that good in late, you could throw away the whole game.
Dont be dissapointed with yourself if you get feed and lose, not every game is meant to be won, you will eventually climb if you keep playing good consistently, dont flame or expect others to do what you tell them, sure you can just ask them to stop dying, give some advice or try to make a call, but if they answer aggresively, report them and the game will mute them for you. After every game think, what could i have done better? where i can improve? Something that have helped me a lot with league mentality was to read the Art of War from Sun Tsu, its amazing how a lot of aspects of the book can be found in league, like the 5 things a good general should have in mind, when to be avoid a strong enemy and when to act weak, when to harass and when to defend, what is up to you and what depends from the context/environment/enemy, etc.
Also there are a few streamers that had teached me a lot about league and sett, like xPetu with macro, Autolykus with Sett and Kerios allowed me to learn what every champ does. Hope this helps anyone, and feel free to share some insights about certain matchups/builds!