League of Legends is one of the more recent supernovas in the world of online RPGs with a loyal and fervent community, a knowledgeable development team that has a good appreciation for character balance, and with one of the most unfortunate acronyms on the entire internet. LOL was launched in late October of 2009 by Riot Games, and has capped 32 million users as of this writeup, although it's true that duplicate accounts are almost obligatory on the site. That's probably because signup is free. And even though you could theoretically just throw money at the site and buy your way into its features and perks, there isn't a lot in the game you can't access the old hard way if you've got willpower, modest skill, and spare time out the ass. Here's a brief overview:
Leveling, Champions, and other out-of-game prep
The game has many familiar characteristics to versed and ventured gamers. It's level-based, with summoners(users) gaining XP from battles and leveling up once they pass certain XP thresholds. You still gain XP from defeats, but not as much as you do in victories, as would be expected. XP distribution and leveling is exponential, and summoner levels cap at level 30. The other two points systems in LOL are Influence Points and Riot Points. The IP system is distributed and scaled in a way similar to XP, even though you still continue to be rewarded IP after you cap at level 30 as a summoner. IP is more or less yo' moneys in this game. More than anything it's used to purchase champions, and also to purchase runes, which I'll address later. Riot Points on the other hand is basically the shortcut system, because the only way RP can be gained is by purchasing it through Riot Games, hence the name. You can use RP to buy champions, or to buy skins for champions you own. Skins are the main thing you can't just purchase with IP, and the only truly justifiable reason for purchasing RP. Most people who throw money at RP are either impatient, or actual seasoned veterans who can't get much better anyway, or maybe just despicable good samaritans who like to support their favorite sites. I don't really know their intentions but I'll probably judge them either way whether I feel good about it or not.
Runes and masteries are basically the way you customize and specialize your champions abilities to give you an edge before the match even begins. You can have multiple pages to compliment your different play styles. Runes can only be purchased with IP, and mastery pages are built by a points system based on your summoner level. A level 17 summoner has 17 mastery points they can distribute on any given mastery page, etc. They often, in fact usually make the difference between a win and a loss by the time you reach summoner level 12 or so.
The characters that make up League of Legends are called Champions and bring different skill sets to the table for their teams, and suggest certain play styles, though many champions have different build options and bleed into several different categories. For example, Ezreal is a character that's typically built as an AD character (melee fighter), but sometimes people choose to build him as an ability power character (magic damage) to throw their lane opponents off guard. Or just to have fun. Or both. But all the same, specific styles of play are implied by the nature of different characters. Obviously, some are more OP than others, but no character is impossible to counter. The development team at Riot is constantly changing the abilities and skill levels of champions in patch updates through buffs and nerfs to try to maintain a balance in the character pool. In draft games, counterpicking is a large part of the strategy to building a team. In many instances when a certain level of skill is reached amongst players, it's easy to tell which team will win a match just based on the balance and strength of the champions they've selected.
The most basic and major classifications of champions are in their fighting styles:
Carry - The champion that the team is centered around, the main source of damage output and leader in team fights. Should be getting the most kills, should have the most powerful build, should get their team out of the stickiest situation, and should basically 'carry' their team to victory. Can be built as AD or AP.
Support - Self-explanatory. A character that's designed to hang back and support the team, ideally by healing them or giving them mana, slowing or stunning or otherwise preoccupying enemies, should ideally have many assists but few kills. Needs to have a very strong sense of map awareness and selflessness.
Tank - Familiar character scheme to many gamers, a tank is a character that's designed to move slowly and attack modestly, but more than anything is designed to take a fuckface of damage in team fights and live to tell the tale. There's a big difference between 'being' a tank and just building tanky(lots of armor).
There's also another specialized kind of character, a jungler, which I'll explain in a minute.
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Gameplay
The objective of a classic game of League is to help your team pierce the enemy team's defenses and destroy their Nexus before they do the same to you. Typically, champions will start in a lane, fighting against other champions for control of their lane. In the game, constant waves of mindless minions are sent to attack the enemy for each respective lane on the map. By killing these minions, champions receive bonus gold which they can use to more quickly buy items from the shop towards their builds. Though, you only get credit for the minion kill if you get the last hit in, so it's a skill in and of itself to not let anyone else get your minion kill. The act of building up minion kills to harvest as much gold as you can is referred to as farming. Even if you don't farm though, for whatever reason, (like if you're playing support and letting your lane partner take all the farm(good idea)) you still gain gold continuously throughout the game after the first minion spawn. You also start out with a certain amount of gold every match. It's typically 475, but there are abilities and masteries that can boost this. You can also boost the rate at which you automatically gain gold through masteries.
Each lane is divided equally in half on the map and is protected by a series of turrets pushing back in layers to each team's base. Turrets are very strong, and will kill just about anything if you give them long enough, including champions. They're far from indestructible though - the main objective in a classic game is to destroy the turrets in any given lane to clear a path to the enemy's nexus and destroy it. Turrets can only attack one target at a time, and will lock in on a target and continue to attack the target until the target is either destroyed or out of the turret's range. This includes your minions though. Once you've pushed out the enemy champions in your lane pushed your minion wave to the turret, you're free to help your minion wave attack the turret while the minions tank the damage. Don't feel bad about it though, they're literally meant to charge and die and that's it. You probably won't be able to take down the turret's health all the way and destroy it the first time you're able to attack it though. It takes time, tactics, precision, and well-timed pressure. Any team that can knock over a turret in the first 8-10 minutes of a 5s match is doing a damn fine job.
Before the start of the game in the champion selection queue, you are allowed to take two summoner spells with you into battle from a short list of spells that help champions in various different ways, depending on their strategy and style of play. Some of the spells are available immediately upon opening an account, most are summoner level-based. By the time you've reached level 12, all summoner spells will be available to you.
At the beginning of the match, your champion starts at level 1, and is granted a spell distribution point. Every champion has 3 basic spells or abilities, activated on the keyboard by pressing the q, w, and e keys respectively. Each summoner has a different set of spells, though many character schemes have similar sets of basic spells to them. You gain Experience points through your exposure to kills, through minions or champions, in your lane. It doesn't matter whether or not you actually get the kill - if you're in proximity to an enemy minion or enemy champion's death, you gain XP. You also gain XP and gold when your team destroys a turret, regardless of where you are on the map. As you get more experience in the game, your champion begins to level up. Each time your champion levels up, you're allowed another spell distribution point for your q, w, or e spells. You must level up each spell at least once before you can use it, and each other leveling up of the spell will merely improve its power or efficiency. You can't simply max out any one skill by adding your spell distribution point to it every time you level up. The game will make you alternate between the spells you level up until you've eventually distributed all your spells evenly. Once you reach level 6, you can unlock your character's ultimate ability(ult, colloquially), which is cast by pressing the r key. Ults are highly unique, and usually what will make or break fights between other champions. With most characters, you'll want to level up your ult as much as possible. Your 3 soonest opportunities to level up your ult come at levels 6, 11, and 16. Once your champion has reached level 18, it's maxed out, and all your spell distribution points will have been distributed evenly - 5 levels for q, w, and e, and 3 for r.
Spell casting isn't exactly an unlimited thing though - many spells cast mana to cost. Your level of mana you have depends on your character, your level, and your build. There are some mana-less champions out there that require no mana to cast any of their spells or activate any of their abilities, and they are pretty fuckin cool. Mostly. Though, regardless of how much mana a spell costs to cast if any at all, all spells have a cooldown time in which you can't cast the spell again until it cools down. Typically, the cooldowns for your q, w, and e won't be too draconian. But most character's ult abilities have a pretty long cooldown associated with them. Unless your name is Kassadin. Riftwalkin all ova' tha' fuckin place! And yeah, there are some others with low cooldowns too, just not many. Your mana regeneration and cooldown times are both things you can improve through builds, if your play style and champion style necessitate them.
All champions also have at least one unique passive ability that remains constant throughout the game. Passive abilities can also be added to the character through certain items. There are even a few items that will grant your champion a new activated ability (Quicksilver Sash, Zhonya's Hourglass, some others). These are generally pretty expensive though. So farm up!
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Fields of Justice, jungling, Dominion
In League of Legends, matches are fought on The Fields of Justice(maps). In classic gameplay, there are two Fields of Justice to choose from: Summoner's Rift and Twisted Treeline, aka 5s and 3s. As implied, Summoner's Rift is a map designed for 5 summoners and Twisted Treeline is designed for 3. Summoner's Rift has 3 lanes (top, bot, mid) and Twisted Treeline only has 2. Typical game length in 5s is about 45 minutes, 3s is closer to 25 or 30. That's not to say you can't have a 70 minute game or a 12 minute game in either. Shit happens. Especially amongst heroes. With weapons. And egos. You saw this in mythology all the time.
I digress. The space beyond the team's main base that falls in between the lanes is known as the jungle. The jungle is full of naturally neutral jungle creatures that will attack you if instigated. There are many benefits in ignoring lane play and focusing only on the jungle creatures for your farm. This process is known as jungling, and the characters who specialize in it are junglers. Or at least they were. Instead of explaining how the jungle used to be before the massive overhaul a few weeks ago (or masturbating about how much better it was before they fucked it up made it more accessible), I'll just explain the way it works now. At this point, every jungle creature gives you some kind of temporary buff that you can use to help you in battle. Leveling up by fighting jungle creatures is pretty slow now, and isn't as reliable as traditional laning. But it can still be done. The main purpose of a jungler in terms of the team is setting ganks. If there is any part of the map that isn't being occupied by you or an ally(including your minions), then you can't see exactly what's happening in that part of the map. The temporarily invisible parts of the map are referred to as the fog of war. When a jungler is out of jungle creatures to kill, it will often roam into a lane where two or more opposing champions are fighting each other, and assault the enemy champion. The act of sneak-attacking a champion in a lane that you weren't previously laning in is called a gank. It's an important part of the game, and it's the reason why it's very important to have a good map awareness, and to have the location of all your enemies accounted for at all times. A good jungler can make all the difference in clearing lanes to take down turrets in the early stages of a match.
One last thing - a variant of League of Legends that was released in September of this year is called Dominion. In dominion, two teams of five play on a map with 5 capture points spread out like a starfish. There are no lanes, few jungle creatures, the gold regeneration is quicker, the builds are quicker, the demand for map awareness and split second decisions is higher, the necessity of team organization, communication, and cooperation is higher, and it just gives a much more wide open and adrenaline filled experience to the game. Basically it's a 95 mile-an-hour clusterfuck. Try it some time.
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Jargon:
Farm - Collecting gold, most typically by killing minions in your lane.
Gank - An ambush, basically. Successful ganks result in champion kills.
Jungle - Can refer to the jungle, the area between lanes covered by fog of war, or the act of jungling, to stay primarily out of lane and build your character up by killing jungle creatures, roaming, and ganking until later levels.
Jungle Invader - A jungler who has a knack for stealing jungle creatures from their opponent's side of the map
Carry - Leader of a team, who ideally 'carry' their team to victory
Support - Character that provides support in team fights or 2v2 laning.
Feed - To continuously be killed by other champions. Used sarcastically by the LOL community a lot. (ex: Report Teemo for feeding/lolsurf I agree, report/Teemo uninstall plz)
Dive, or Turret diving - to attempt to kill a champion by diving within the range of a turret and taking the damage from the turret as you're pressing your attack. Can also just refer to attacking the turret directly without any minions around you, mostly just done by intentional feeders.
Intentional feeder - Trolls, and assholes, that die to help the other team.
Smurf - Duplicate account, often made to play with friends you're introducing the game to, or just to fuck around.
MR - Magic Resist
AP - Ability Power, determines effectiveness of spells
AD - Attack Damage
AS - Attack Speed with autoattacks
KS - kill steal
OP - Overpowered
AOE - Area of Effect damage
CC - Crowd Control (stuns, taunts, fears, slows, etc)
MIA - missing in action, when an enemy champion isn't seen on the board in the lanes your team is fighting with, usually means they're getting buffs, or even worse, on their way to gank someone on your team
Squishy - opposite of tanky, relatively easy to kill, especially early game when you haven't built any health, MR, or armor
Sustain or Lane Sustain - your ability to constantly stay in the lane to push, defend, farm, kill your lane opponent, whatever you need to do to be doing your job, without having to constantly retreat back to base. Hand-in-hand with squishiness.
Roamer - Mobile characters who don't necessarily stay loyal to one lane. An aspect of junglers, but doesn't necessarily denote a jungler. Can be a tank and/or support.
Bush - tall grass spread throughout lanes and the jungle in which champions are invisible if they're the only ones occupying the bush.
Face-check the bush - Occupying the bush by diving face-first into it. Often results in you getting your face blown off.
Nerf - Decrease of a champions power and abilities by the development team in a patch update.
Buff - Opposite of nerf, increase in ability in a patch. Can also refer to the temporary abilities gained by killing jungle creatures.
Fog of war - Invisible part of the map where none of your allies are there to illuminate it. Typically 70-80% of the map is in the fog of war at any given time.
n00blord - One of the more infamous inside jokes in the history of League of Legends. Get dunked!
And that's the gist of it. I recommend this soul depriving time vampire. It's most fun with your nerd rage-y friends, as long as you're good enough friends that you can shout at them for being retarded enough to build sheen on Soraka or going solomid Tryndamere :)
(edit note, July 27, 2012: removed list of champions, it would be quite a chore to keep constantly updated with 2-3 new champs every month. Flip your upvote if you want.)