Summary:

1. Introduction
2. Why you should play off-meta
3. Laner Kayn Pros/Cons
4. How to play

1. Introduction

Hello! I'm brazilian and I am not a competitive player, I like to play for fun with off-meta builds with my friends.

I usually play against gold/platinum and like to test new items and runes combinations that are not usual for the champions. Why I do this? Because it is fun, and you know what is more fun? Stomp big ego gold/platinum players with off-meta builds and piss them off!

Anyway, I played Kayn a lot and I really like this champion, but I hate that he gets a weak early/mid game being a jungler because of the XP gap between top/mid laners and junglers that doesn't allow him to show his full potential (and because of the time it takes to stack his passive) so that's why I began playing laner Kayn.

2. Why you should play off-meta

I want people to stop caring about having a high elo just to be accepted as a good player, I want people to play for fun.

Most people that play league don't even enjoy the game, they are just addicted to it and just care about climbing ranks as if it matters to their lives, but at the end of the day in the real world, nobody gives a f about your league of legends rank, so go have a fun time as you should do and use /muteall, this will be better for your mental health.

3. Laner Kayn Pros/Cons

PROS:

+ Huge early damage
+ Stacks faster
+ XP Advantage
+ Wins against the majority of melee champions
+ Can dive easily with R
+ Can pass through minions with his E
+ Great wave clear and tower damage

CONS:

- Weak against ranged champs
- High mana usage (no blue buff)
- Will always transform into Rhaast, blue form is weak against the majority of toplaners (bruisers/tanks)

(AGAINST MELEES)

Start with Corrupting Potion or Doran's Blade and a Health Potion.

You will use your Q to farm minions while doing damage to the enemy, you win the majority of early trades just trust your damage (see the Threats chapter).
As you trade against the enemy laner, you will stack your PASSIVE. If they are melee, you will get Rhaast stacks, he is the best transformation option for toplaner Kayn.

If you have the Demolish rune you need to focus the enemy tower, you will deal massive damage to it.

At level 7 you will probably have the Rhaast transformation ready and half of your Mythic item, so you will be very strong, being able to solo the enemy laner or help your midlane after pushing top wave.

You will be a great split-pusher and also help a lot at team fights because of the Rhaast form (just don't bee TOO crazy).

(AGAINST RANGEDS)

Start with Doran's Shield and Health Potion.

You will have to play very safe, instead of starting with Q, start with W to poke the enemy and evade trades, use your Q and E to escape. Wait for your jungler so you can kill the enemy.
As you poke the enemy, you will stack your PASSIVE. If they are ranged, you will get Shadow Assassin, but he still isn't very effective against usual toplaner rangeds (Quinn, Vayne, Gnar), so you will probably want to give up on your lane and wait for the Rhaast form to help your team (you will still be able to kill the enemy when you have ult).

At level 9~10 you will have the Rhaast transformation and half of your Mythic item done. Focus on guarding the Dragons and split-push botlane.

You will guarantee the Dragons for your team and help at team fights.