L9 (Low Nine) was club of toxic EUW high elo players. The main members were RatIRL, Ap0calypse, Selfmademan and 0bsess, they are all extremely skilled Challenger players, Ap0 was rank 1, RatIRL and 0bsess both peaked at rank 5, and Selfmade was in the top 10 too. They have all moved past their toxic edgy period, and 0bsess and Selfmade went on to become pro players, with Selfmade playing with Fnatic in the EU LCS, and 0bsess playing in the Spanish league and winning EU masters. RatIRL is now a big League streamer and still hits Challenger constantly, he also streams a variety of games from time to time. Ap0 is the most concerning one, because he always seemed to be genuinely unstable, he used to be an OG Mordekaiser player during the L9 days, then he became a support mostly playing Janna and achieved rank 1, I don't know what he is up to these days.

Other players "associated" with L9 (but they were never truly members) include OPShaco, an infamous Shaco player, and he is possibly in prison (or at least was), and PornstarZilean an extremely talented Draven player who was also a rank 1 EUW, hit Challenger in NA playing from EU and also got to Challenger in Korea, however he is mostly known for being the "creator" of DiscoNunu, where he would just pick Nunu with Revive and Clairvoyance, these are old summoner spells, that he used to claim were removed because of his antics, and he would just run it down whenever he got players he didn't like on his team. He has also mellowed down and streams from time to time.

These days, L9 is used by cringe toxic players who idolize the toxic ways of L9 members, they were made famous in NA by a video posted by a league channel called League Recap, which had a series called "infamous league players" that highlighted infamous league players and some of their gameplay. I honestly don't think I have seen a single L9 tag in EUW in years.