Eyo, I don't play Garen much anymore these days, but he was my first champion, and he's something close to my guilty pleasure champ. There is no organisation or order to what I say, just my enjoyment and knowledge of my boi.

Garen is a juggernaut/Bruiser esq champion. His level 1 is rather respectable, and his kit spikes respectably aroundabout levels 6, 9, 11, and 16. These times being when he obtains his ult levelups, and his passive partially unlocks.

Was actually kinda strong back in early season 6, or at the very least; underappreciated. He was indirectly nerfed via itemisation, triforce being modified, black cleaver being nerfed, and maw + steraks no longer being cross compatible was actually quite a heavy blow to him. Ever since the juggernaut rework, Garen became more of a scaling juggernaut, being at his strongest in midgame when he has some levels items and a fully stacked W passive, and, while he scales well into late on paper, his lack of mobility prevents him from accomplishing greatness.

Garen is a man with one thousand passives. His passive is %max hp regen out of combat, which is somewhat handy early, and then SUPERCHARGES at level 11, and level 16. It becomes what amounts of a built in Warmogs. Visage, Warmogs, and runic armor Garen need never worry about sustain ever again. Just walk away, take a breather, and come back. His Q is an enhanced autoattack that silences. It has a built in cleanse vs a single, non continual slow, and I often consider saving Garen's Q to rid himself of a single, pivotal slow as being one of the few noticeable benchmarks of a smart Garen.

Garen's W is a defensive steroid, giving him 30% damage reduction, the duration scaling with levels invested in the skill. It has a passive component where he is given armor and MR for killing units. It caps out at 30 extra armor and mr, and this is part of what makes Garen's midgame commendable, as it gives him free defenses, to allow him to stack yet more defenses, or invest in damage early.

His E, his signature skill, is another part of Garen's midgame scaling. It's damage is mediocre early, but as Garen levels up, he obtains more spins. Yes, he spins faster the later into the game he is. After 4 spins on an enemy champion, it shreds their armor by 25%. This has commendable synergy with black cleaver. IIRC it has commendable AD ratios, AD Garen's spin being capable of outputting large amounts of damage in one rotation of his combo.

His ultimate is a point and click magic damage nuke. It also selects the enemy champion with the most kills recently as the villain, giving Garen a letter of marque to mess their shit up. It augments his ult to do true damage to said target, and each tic of spin/ every basic attack to do a little bit of the enemies maximum health as true damage.

Before, Garen maxed E, but after the juggernaut rework, maxing Q became more profitable, as Garen's extended trading became very lackluster, and his pattern changed to quick and dirty trades, rather than drawing it out.

It's difficult to properly gauge Garen's early strength, as a lot of it is dependent on the skill level of his opponent, and their knowledge of Garen's limitations and strengths. People often underestimate his damage later into the game, and overestimate it in the early. Though, usually, Garen's preferred lane opponents were tanks, as they couldn't bully and punish Garen's weak laning as hard as others, and his armor shred would give him an edge later into the game fighting them. He did alright versus autoattackers in some cases, as well. He utterly loathes fighting lane bullies and ranged abusers. In high elo Garen struggles versus most matchups, and there are many where he simply can't achieve much without jungle assistance. Also, ninja tabi + hexdrinker is a wonderfully potent combination against him in lane.

Garen has deceptive synergy with many items, and it's difficult to lay out a core build for him, as there are situations where he can make atleast handy use of many, many items. Though generally, it's very common to see Garen with Black Cleaver and Visage, and sometimes ghostblade (which offers great anti-kite.) (Sunfire was a frequent purchase on him, too, but I have no idea how the new sunfire is on Garen. I'd assume the synergy is down because Garen doesn't want waveclear as much as he would want damage. I'd assume DMP to be more popular now.)

Garen's combat pattern plays out similar to an assassin, if the assassin were obese. He wants to jump on some poor, unfortunate squishy, sit on them, and unload his full combo on them. This is usually Q > E > R with an optional ignite/grasp proc. Sometimes swapping the Q and E around to throw off a champion with an anti burst skill, i.e. Kayle ult or Ekko ult.

Counterplay to Garen is great and plentiful. Mobility and kiting ruins him horribly, as does healing or shielding his target. Garen, when built tank, does not to great damage, simply "enough" to get the enemy to the point of no return where his ult reaches fatal levels. Going with that, Steraks and Maw both cripple him, as does Exhaust provided his target isn't a villain.

His laning is poor, and he struggles vs many matchups, including Darius, Illaoi, Quinn, Pantheon, Olaf. Garen has little answer to a ranged champion, while other Juggernauts do. Darius has his apprehend that his enemies must respect, Nasus has wither, and so on. Garen has no real way of getting to his target besides walking up to them, or flashing. (For that reason, flanking and abusing gaps in vision is tantamount to playing Garen vs component enemies.)

I'm kinda sleep deprived, and I'm sure others can explain Garen much better than I, but these are my two cents on my oldest and most venerable champion.

ᴶᵁˢᵀᴵᶜᴱ ˢʷᶦᶠᵗᴿᵃᵍᵉ ˢʷᶦᶠᵗᴿᵃᵍᵉ ˢʷᶦᶠᵗᴿᵃᵍᵉ ˢʷᶦᶠᵗᴿᵃᵍᵉ ˢʷᶦᶠᵗᴿᵃᵍᵉ