Champion Classes Riot has given up on. Episode 1 AD MID LANE assassins
So league is a 8 year old game, dependant on what you consider league of legends, alpha, beta, season one, season two, but regardless, game is pretty old. So because of that, their are some themes/classes riot has invented that they clearly have no intention of ever creating again, or at least any time soon, at the very least, rework the ones that already exist. So here I want to make a list of some classes/themes riot has had, that they no longer create, show when the last one was created, and why they will most likely not revisit it or at least took a break.
1: Ad mid lane assassins.
List that existed:
(yes kha zix was a mid lane ad assassin at one point in time)
List of Current Viable Choices: SORTA
Latest one made: 2013
Defining Traits: High burst, Combo oriented, Lots of mobility. EDGE
What are Ad mid lane assassins? Ad mid lane assasins were once known as the burstiest class in this game, with very strong mobility that was unrivaled by any other class, they were well known for requiring a lot of skill, and could be heavily punished for when they got behind. However after the terror they struck on the rift during season 3 and 4, which was hailed as the golden age for assasins and mechanical mid laners we have seen riot take a huge back step away from the assassin class, and even down right drop the idea of mid lane ad assasins. The latest one that was ever released, that had the clear goal that he was suppose to be a mid lane AD assasin/bruiser hybrid, was Yasuo. This was 2013, we are in 2018. That means riot has quite literally spent five years avoiding the class. Hell Even 
stands as the newest AD assassin jungler since the release of 
and and they were created in 2012. So going off those numbers. Yasuo was the latest AD assassin PERIOD to ever be created until riot made Kayn, and even with the release of Kayn it was clear he had very set rules and requirements of things that must be done before he can kill you. Having something many streamers noted as "the possible new mind set for riot and how assassins work" And if you want to go extremely deeper the last directly intioneal AP assassin for laners to be released was 
in 2015.
Why has Riot Left this class: Well to be honest it's most likely because the role itself doesn't fit the vision Riot has for the game. In general riot has the following views currently in how each lane should function, be picked.
Top Laners: Should be either tanks, bruisers or Juggernauts with the very rare carry focused champion, when a mage is released that can play top lane, Rumble, vlad, swaine, they share the trait, that they can be fairly tanky.
Jungle: Are either cc tanks, or bursty assasins, and even the assasins have the options to build tanky builds if required. Riot has made it very clear, with the exclusion of Marksman junglers, a role we will talk about in another episode, that Junglers are meant to be close to the front.
ADC: PEW PEW PEW 
Not even going to get into detail on this one.
Support: Either tanky front liners, or enchanters with strong shield based abilities. The occasional mage buddy like brand or lux.
Mid also has a clear vision riot has for it. Mages, supports and the occasional mid lane assassin that gets released every so often (when you include both ad or ap) but if you start counting.
Mages Supports Ap Assasins Ad Assasins
that's 3/4th of it being AP champions. So it's clear at this point, riot wants mid laners to be AP focused. When they invented the Ad assassin class, it was clear their intended placement was to be in the mid lane, but with the release of Kayn, it's made even more clear, that most likely any AD assasins that get invented in the future, will be put in the jungle.
So we have our answer, riot wants mid lane to be AP focused, they will try their best to keep the ones we have now in proper balancing, to not forsake the fans of such champions, for once a champion is created and released, their really is no going back, the most you can do is a rework, but once a champion is here, they are here to stay. So riot has no choice but to keep Zed and Talon in a decent spot, at the very least they can't out right delete them. But back to the topic. Why has riot basically silently said "all mid lane champions should be doing AP damage"
Well if you go to one of the oldest games ever, DND, to than go into one of the oldest MMORPGs ever that stands as the stone pillar of MMORPGS, WoW. We have something called a "raid party". A raid party is a group/team of heroes that ventures forth to accomplish a mission. A raid party consists of one or two tanks, a healer, some form of ad damage, and a mage. The two things that are ALWAYS visible in a raid party is a tank, and after that a mage. These are always present in a DND party or a mmorpg raid party, and while parties can fluctuate and get creative, tank and mage were the two constant things that are left un argued. But once again, while history is a useful tool, why is it mages are left a common theme in a raid party? To put it simple, it all has to do with stats.
MOST GAMES separate magic damage and Physical damage as two separate things. So because of this in MOST GAMES monsters will have really good armor stats to deflect physical damage, but sub par magic resist stats to deflect magic damage. So, in games, magic damage, was simply meant to be reliable damage that you can count on and when you look at most ap characters in this game, they tend to have very reliable toolkits that are not awkward and easy to balance for they aren't to complicated. Now look what happens when everyone is full AD in a game, the team that isn't gets to have mega tanks, the AD characters relatively do nothing, and the mages laugh as they kill off your team. Full AD comps don't work, and since the large majority of top laners and junglers are also AD champions, if mid lane goes AD, than you end up with a full AD comp.
SO PROBLEM 1 Full AD comps are unreliable and a near sure fire way to lose.
Problem 2 AD mid laners have quite literally left league of legends player base traumatized, and it's been 4 years since they been nerfd to the ground. It is the world war2/Vietnam of league of legends, where some players will remember themselves as heroes, and other players will remember a period of oppression. Some people will go "WHATTTT AD ASSASSINS ARENT NERFD TO THE GROUND, THEY ARE STILL OP PHANTOM YOU SO STUPID KLSD:JF:LKDSJGS" For those who actually been in the game for a while, and know what i'm talking about, they will nod their heads. During season 3 and 4, as stated earlier, it was the golden era of the assassins, and not just assassins but talented mid laners in general. We have a reason why Faker's skin is Zed during season 3 but has been a mage in his other two skins. Think about that for a moment fellas. Why is it, the most famous assassin player in league of legends history, went from Zed, to strictly and only mages after. The answer is very simple. After the nerfs/rework of his favorite assassin, LeBlanc, he simply hasn't played any assasins in pro play, and debate even solo q since. During season 3 and 4, with how balancing, runes, masteries, player mind sets, a list of many things, mid lane was by far the strongest role in the game, not a debate, it was the strongest. No role even came close the carry potential mid lane had and to this day no role ever will again. That was, and simply because, the game you won or lost, was purely decided by who had the better mid laner. The most paid and valued players during those seasons, the most popular players. They were all mid laners, bjergsen, xpeke, faker, westdoor, all were mid laners. This was once again due to the fact, mid lane was a very strong role, so of course your investments should go into the strongest role. AD assassins like Zed, Talon, Yasuo, they did something to the game. They basically invented the term "snow ball". With each kill they got, they became stronger, with each item they got, the more the game felt hopeless, to this day mid lane assassins are recognized as the most snow bally class, and their is some points of truth to it. We have the term "yasuo/zed got fed, gg" for a reason. If a player is compentant on them, they will explode far out of control, they can one v two, hell even one v three if talented enough with a proper lead. We even notice riot distancing themselves from top lane carry roles like fiora and jax.
To put it simple, Ad mellee characters are simply hard to balance. Why? For they have lots of damage. Solution? Nerf the damage? WRONG, if you did that, than you virtually have zero reason to pick a mellee over a marksman or a mage, or even a tank, melee champions simply can't exist without damage. So really we are in this very awkward position until riot re thinks the game as a wh ole and their approach to balance.
Honestly it is very likely we will never see a new mid lane AD assassin ever again and that Yasuo will be the very last one to ever be released. Riot tried inventing a new class in season 3, that was when most if not all the AD mid assassins were created. We saw a final attempt in season four, and after that, nothing.
will most likely remain the most unique..and the only of their kind, as champions who were directly invented and intended to play mid lane in a AD assassin play style.