Lee Sin is a very strong champion. He can excel in plenty of roles, can jungle easily and dominates early game but falls back late game. He has a great abilities which can be used to secure kills/grabbing kills for the team. Lee Sin literally has 7 abilities which all have some really cool tricks which can be used to survive, secure kills, steal objectives, kill steal, etc. This guide isn't only for Mid Lee Sin however, it is for jungle, mid, top and even support Lee Sin!

As a young teen, Lee Sin was intent on becoming a summoner. His will and dedication were unmatched by any of his peers, and his skill drew the attention of Reginald Ashram, the League's High Councilor at the time. While studying at the Arcanum Majoris, Lee Sin became frustrated with instruction paced for the other students. He spent his free time researching the nuances of summoning in hopes of graduating sooner. He made amazing advances in his arcane studies, surpassing all other students. By all indications, he would have become one of the League's greatest summoners were it not for one terrible mistake. Too impatient, he attempted to test his ability by summoning a beast from the Plague Jungles. What he summoned instead was a young boy, but not in one piece. He barely had time to look the boy in what was once his face before the jumbled human mass fell lifeless to the floor. A League investigation later revealed that the boy's entire village was obliterated by feedback from the ritual.

Lee Sin's talents were so promising that the League was willing to overlook the incident, but he could never forgive himself. He left the Institute and journeyed to the Shojin Monastery for eternal repentance, swearing never to practice magic again. Years later, hoping to atone for his crime with martyrdom, he set himself ablaze as a protest of the Noxian occupation of Ionia. He remained alive in this state, enduring searing agony for weeks. His actions paved the way for a League match wherein Ionia prevailed, but by the time he was doused, his eyes had been burned completely from their sockets. Hailed as a savior, he was reborn, and his will to act invigorated. He joined the League of Legends to continue his atonement with sweat and blood, a true monk's only possessions.

Pros
-Strong Early Game
-Strong at 1v1's
-Counters plenty of ap Mids
-Can escape troublesome situations
-Harassment in lane
-Has abilities which give vision

Cons
-Will fall back in late game
-Requires a lot of skill to play
-Not much cc
-He's blind...

Lee Sin is a very complicated champion and takes a lot of practice to get good at mainly because there are so many tips/tricks with Lee Sin. These tips/tricks are:

-Heal using Smite when Iron will is activated, this can help survive in the jungle or survive sticky situations
-Ward hopping/jumping is a very useful trick. Jumping to wards with SafeGuard can help you gain distance over an enemy or escaping. (You can jump to other allied units such as Shaco Boxes, Teemo Shrooms, minions, Zyra plants and even Zyra seeds!)
-Throwing Sonic Wave over walls into a jungle camp and following up with Resonating strike can help you escape
-Take advantage of your ultimate, use it to kick enemies back towards you're team so secure a kill. (Using Resonating strike and flashing behind the enemy champion and then kicking them back means that they will have almost no reaction time at all, also you can use your ultimate to run gain distance when running away from enemies who are chasing)
-Lee Sins q and e will give vision, use this to your advantage when an enemy goes stealth. If they are close to you then use Tempest which will reveal them instantly, or for example if Shaco goes stealth, you can predict where he's running and use Sonic Wave in that direction which may have a chance of hitting him, then follow up with Resonating strike and Tempest
-When supporting as Lee Sin, buy wards as usual. It can help your adc and counter some ganks (Obviously) and can also benefit you as well as you can jump to wards and kick people back
-Follow the enemies flash (Always wait 2 seconds before using Resonating Strike because the enemy might flash over a wall with sonic wave still in effect so you can follow them over the wall)

Combo's= Q=Sonic Wave/Resonating Strike W= Safeguard/Iron Will E=Tempest/Cripple R=Dragons Rage
D= Ignite F= Flash Ward=...Ward

-q,q,e,r
-q,r,q,d
-q,e,d,r,q
-e,e,q,r,d,q
-q,q,ward,w,r,d
-q,q,f,r
Etc

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Thanks all!

SAP Twilly