Okay, so I'm not a hardcore League of Legends (LoL) player, mostly because I don't have a team, and I do have a life. But I really enjoy this game and it's for several important reasons which could all fit under the header contingency. That is, this is a game of shifting, unpredictable, variations in most of the objects the player plays with, while holding constant the map, the goals, and the rules of play.
The actual play of a LoL game is quite straight forward and simple. The mechanics are not particularly difficult to master in the game itself, and the play of any particular champion is limited to basically four action key choices, six if you count the summoner spells. This means learning to play at the most rudimentary level isn't difficult. [What can make it difficult are the other players, some of whom are rude and overly critical. That's not the game's fault; that's the company's fault, and they've taken major steps to control it and it has worked IMHO.]
The game is a PVP team game, and this is one big part of what makes it intriguing, complex, and fun. Your characters ideally have a synergy that you can leverage against the other team. This requires some thoughtful choices of what character to play, good communication, and a little bit of studying on the player's part to understand how best to 'itemize' the character during the game (add gear with particular buffs that aid the character's effectiveness). If you like playing the game, this is fun to do. You actually enjoy figuring this all out. If you're feeling especially nerdy, you can study a decent amount of post game stats, generated by the game as an interactive report, after the game ends.
The champion pool was 123 as of December, and I know they've added a couple more (Gnar, Rek'Sai, Bard, for instance). Those champions vary in their orientation. Some are mighty damage dealers. Some are best in 'support' of damage dealers and/or the team as a whole (with shields, slows, stuns, etc.). Some are best 'in the jungle,' the area between the main roadways where you play in 'fog of war' (limited visibility) unless/until you drop wards (which light the immediate area). Jungles roam the map and can show up in any lane to tilt the lane in favor of one side in sheer numbers. What was a 2 v 2 in lane, suddenly become a 3 v 2. You can see why communication amongst the team is critical.
LoL plays more like a card game than a video game. You do not have a stable of characters you've raised, geared, and trained on. Each new game you and your teammates get a fresh, level 1 character of your choice and build that character up over the duration of the game. Like a card game, you may first begin by mastering your own character/team actions, but to win you have to understand the characters on the team you're playing against, how they synergize, and what threats they represent to your team composition.
As you can image, leveling up quickly and getting enough gold to gear up effectively become primary goals, but at the same time you have in-world map-related goals as a team. The game is, basically, a base defense game. Protect your base; burn down the enemy base. These are inter-related goals, but can sometimes be at odds. Do you attack that tower or "farm creeps" (kill minions for gold)? Do you take a tower, or take a dragon (team buffs)?
To make this even more fun, the game changes because the devs. constantly screw with the skill sets and underlying statistics of the champions, as well as the items/gear for champions. They release patches that change what is referred to as "the game meta," base unbalancing, rebalancing, and introducing new aspects. They don't announce anything; the player base, especially the pros, figure it out and shift their play. A few patches back, everyone favored Braum as a support. Now he's rarely played. For at least a year, no one really played Hecarim. Suddenly he's the the go-to pick for top lane. Lulu was a great support in bottom lane, then a great 'poke' in midlane. Now it's common to see her in top lane. The changing meta, and a team's ability to suss it out and adapt to it affects their success. And...it keeps the game fresh, intriguing, and fun.
To get a sense of this wonderful moving feast, I recommend you watch a pro game, and it's an upset.
