The Pokemon League

The Pokemon League is the final trial you must overcome to 'beat' any Pokemon game, and it works a little differently than previous challenges. In the Pokemon League you must face five powerful trainers in a row, without breaks or access to a PC. Lose to one and you're sent back to the beginning. Each member of the Elite Four is a little stronger than the last, and, like the gym leaders that followed them, each uses a particular kind of pokemon. You need to tailor your team to best these pokemon, then heal up in preparation for the next person in line. 

In short, the Pokemon League is not easy. Wouldn't be the final challenge in the game if it was, y'know?

Sidney, the first member of the Elite Four.
He sure loves him some dark-types.
Elite Four Sidney

Your first stepping stone is Sidney, a dark-type user. Sidney's pokemon aren't terribly durable, but they tend to be faster-than-average, and can hit pretty hard. Fairy-, bug-, and fighting-types are solid choices; psychics and ghosts must stay away. His team consists of the following:
  • Mightyena, level 50. Mightyena starts off every battle by Intimidating your lead pokemon. Annoying if you rely on physical attackers. Otherwise, this guy isn't much better than the Mightyenas you fought so often when tackling the villainous team. Wipe it out before it can use Swagger.
  • Shiftry, level 50. One of Sidney's more annoying pokemon. Shiftry will typically start with Fake Out to get in a cheap free hit, then maintain the offensive with Extrasensory and Swagger. Try to kill it quickly with a powerful bug-type move.
  • Sharpedo, level 50. Incredibly fast, and has some severe hitting power with Crunch, but doesn't bring much else to the table. Put out something with decent defences and you should be able to one-hit Sharpedo with one of its many weaknesses (electric, grass, fighting, fairy, etc). Just watch out for Rough Skin, as it can chew up a decent amount of your HP if you use a physical move.
  • Cacturne, level 50. Definitely the chink in Sidney's armour. Cacturne can hit really hard, but it's incredibly slow and has poor defences. Wipe it out quickly.
  • Absol, level 52. Sidney's powerhouse. Absol can hit incredibly hard with Psycho Cut, Night Slash, and plain 'ol Slash. It's not terribly durable, though, and one fairy-type move will wipe it out in most cases.
Reward: $8,320

Phoebe, the second member of the Elite Four.
Looks like a grass-type? Nope. Total ghost-type. Hardcore.
Elite Four Phoebe

Next up is Phoebe, a ghost-type user. Phoebe's pokemon vascillate between slow 'n bulky and fast 'n paper-thin. Dark-types are fantastic at ripping her lineup apart, but they're better off if they don't rely on physical attacks. Special attacks (Dark Pulse, for example) will work better. Your own ghost-types can also tackle this gym, but you're putting them at an awful risk. Her team consists of the following pokemon:
  • Dusclops, level 51. A poor start, not because Dusclops is amazingly difficult, but because it uses Pressure to force your to use double PP. Bah. Dusclops can get pretty annoying with Confuse Ray, and Curse can murder one of your pokemon, so try and wipe it out in one hit with a strong dark- or ghost-type move.
  • Sableye, level 51. The oddball. Sableye has a variety of decent moves, but it doesn't hit hard enough to make itself a credible threat. The exception is Foul Play, which can mangle physical attackers since it draws on their own Attack stat. Send out a dainty fairy-type to wipe it from existence.
  • Banette, level 51. A fairly standard ghost-type, toting Shadow Ball. Banette is mainly annoying if it sticks Grudge on you and wipes out the PP of one of your better moves. Nevertheless an easy kill.
  • Banette, level 51. A bit more annoying, as it uses Will-'O-Wisp to burn your pokemon. Try to take it out before this happens. Otherwise, basically the same as the previous Banette, and easy to wipe out in one hit.
  • Dusknoir, level 53. The big threat on Phoebe's team. Dusknoir sports some painful and surprising moves - Ice Punch and Fire Punch are weird inclusions for your first trip through Phoebe's ranks - and it takes so long to kill if you can't target its weakness. Debilitating moves are a big plus if you can dish 'em out in this battle.
Reward: $8,480

Glacia, the third member of the Elite Four. Chilling.
Elite Four Glacia

True to her name, Glacia specializes in ice-type pokemon. She loves moves that will freeze your pokemon, and it seems to happen more often than you'd like. Worse, some of her ice-types don't have a weakness to fire. Yeeks. Fighting-type pokemon excel against her line-up, and given her pokemon of choice, electric-types aren't bad either. Her team consists of the following pokemon:
  • Glalie, level 52. A straight-up ice-type, Glalie will always begin the match with Hail to deal incremental damage. It'll then lay into your pokemon with Ice Shard, and, occasionally, it'll set up a Light Screen for its team. Brick Break is an ideal move for wiping out this pokemon, especially if it managed to put up Light Screen.
  • Frosslass, level 52. Frosslass likes special moves, and usually tries to wipe you out with strong-but-inaccurate Blizzard. It will also renew Hail, if need be. A solid physical dark- or ghost-type move - Crunch, maybe? - can take it down in a hurry, as its HP sucks.
  • Froslasss, level 52. This Frosslass acts pretty much identically to the last one. Use the same tactics to beat it down.
  • Glalie, level 52. Hey, this looks familiar. The second Glalie likes to stall more, and uses Protect often. Expect it to waste a fair number of your turns while you try to bring it down like the first.
  • Walrein, level 54. This big lug tends to spam either Blizzard or Surf, depending on your pokemon. Pray for the former, as it misses fairly often. Walrein has a marked resistance to fire, so you'll have to target its ice-type with steel or fighting. Electric-type moves can also work well against its water-type half, but don't even consider bringing a grass-type into the fight.
Reward: $8,640

Drake, the head of the Elite Four. He are teh dragunz.
Elite Four Drake

Drake is a dragon-type fanatic, and his team is an absolute powerhouse befitting the majesty of his type. Every member of his team can hit damned hard, and they can cover a wide variety of weaknesses. Fairy-types can clean up against Drake, as can ice-types; other dragon-types may struggle unless they have a speed and power advantage. His team consists of the following pokemon:
  • Altaria, level 53. Probably the weakest of Drake's pokemon, but it can still put a dent in you with Dragon Pulse. Ice-type moves are doubly effective against Altaria, and can clip it quite easily.
  • Kingdra, level 53. Though it doesn't hit that hard, Kingdra sports some powerful moves, particularly Surf. It can also put you to sleep with Yawn, which is problematic since, unless you have a dragon- or fairy-type move at the ready, you probably won't take it out in a single round. Make sure those moves are primed and ready.
  • Flygon, level 53. Mercilessly fast, this Flygon is obsessed with using Boomburst, an admittedly solid move. An ice-type move can wipe it out very quickly, and dragon-type moves are pretty decent as well. (You'll also make it quite impotent by deploying something with Soundproof, such as an Exploud.)
  • Flygon, level 53. Quite as fast as its fellow, this Flygon is more dangerous since it likes to use Earthquake. A lot. Bring out a flying-type to mitigate the effects of Earthquake, or move quickly to wipe it out in a single hit before it even uses Earthquake.
  • Salamence, level 55. Threat number one in Drake's team. Salamence has some crazy defences, and is more than capable of wiping out vast swathes of pokemon with Dragon Rush and, less often, Thunder Fang and Zen Headbutt. Ice-type moves are ideal for four-times damage, while bringing out a fairy-type will negate the effects of Dragon Rush.
Reward: $8,800

As if this surprised anyone.
Champion Steven

The end of the line. Steven is a steel-type specialist, which means that his pokemon have ridiculous defences, particularly in the physical category. Even the strongest of fighting-type moves may struggle to pierce his defences, and several of his pokemon can counter fighting-types anyway. Fire-types are pretty good against most of Steven's pokemon, and ground-types don't do too badly either. His team consists of the following pokemon:
  • Skarmory, level 57. These things are always a pain, and Skarmory makes itself doubly annoying with Spikes and Toxic. Steel Wing is painful, as well, though it's almost an afterthought. Fire-type moves (FLAMETHROWER) will crisp this bird, and electric-types are just as good. You want to wipe Skarmory out before it deploys Spikes, or at least have an anti-Spikes countermeasure ready (Rapid Spin!), lest you have to put up with the stupid things chewing at your health for the entire battle.
  • Aggron, level 57. Ridiculous defences, and some hideously powerful moves, like, oh, Earthquake. Always with the Earthquake. (Iron Tail and Stone Edge, too, but they're less accurate.) Fortunately, Aggron is just about the slowest pokemon on the planet, and you can easily wipe it out with a single Surf. Fighting-type moves aren't bad, either, even if they're physical, as they'll do four-times damage.
  • Cradily, level 57. Less on the outright offence than most of Steven's team, Cradily will either try to absorb your team to death or use Confuse Ray and Sludge Bomb to chip away at your health. Ice-type moves are pretty awesome here.
  • Armaldo, level 57. A pretty powerful pokemon with X-Scissor, Metal Claw, and Slash, but ultimately one of Steven's lesser threats. Water is a prime choice.
  • Claydol, level 57. Claydol is a utility setup for the final members of Steven's team, and will start with Reflect almost every time before switching to the offensive. After that, expect Earth Power to rule the day. Another so-so pokemon that you can usually wipe out with water- or grass-type moves.
  • Metagross, level 59. Here's the big troublemaker. Metagross is strong enough on its own, but Steven will change it to Mega Metagross, bolstering its attacks. It will then proceed to paste your team with Zen Headbutt, Meteor Mash, Giga Impact, and the occasional swift Bullet Punch. Ouch. Fire-type moves are ideal for dealing with Metagross' ridiculous defences, and ground-type moves aren't bad either. You should also consider debilitating Metagross with either a burn or paralysis / sleep - burning is especially helpful, as it'll cut back on Metagross' high attack scores. It sure does like those physical moves.
Reward: $11,800

Defeat Steven and, hell, congrats! You've beaten ze ga... oh, wait, what's this?

Pokemon Trainer Brendan / May
  • Swellow, level 48
  • Raichu, level 48
  • Wailord / Magcargo / Breloom, level 48
  • Breloom / Wailord / Magcargo, level 48
  • Blaziken / Sceptile / Swampert, level 50
Reward: Jack all

This might be a challenging battle had you not just beaten Steven, who is much tougher. The only thing of note here is that your rival's starter pokemon with turn into its Mega form. Tough, yes, but ultimately pretty sad compared to, oh, Mega Metagross. (Also, no experience and no cash reward. Lame!)

Okay, now the game's over. There's still plenty of post-game content, however, and you'll get a taste of it by watching the credits to the end. Once all that's done you can also head to Steven's house in Mossdeep, where you'll find a note - and a Poke Ball containing a Beldum. Sweet. The Beldum is holding an Iron Plate, too, so, double score.

You get one final prize for beating the Elite Four for the first time, as well. Leave your house and walk to the entrance of Littleroot. Professor Birch will be flailing about madly on Route 101, in a dramatic recreation of the beginning of the game - only this time the pokemon he offers you are the Johto starters: Chikorita, Cyndaquil, and Totodile. Sweet.

Rematches

Once you've completed the Elite Four once, you can return here and face them again with enhanced teams. The Elite Four and the Champion now have stronger teams, more pokemon, and Mega Stones, as well, so these battles will be considerably tougher.

Elite Four Sidney

  • Scrafty, level 70
  • Mandibuzz, level 70
  • Sharpedo, level 70
  • Shiftry, level 70
  • Zoroark, level 70
  • Absol, level 72
Reward: $11,520

Sidney's repertoire is considerably stronger, but aside from Mandibuzz their defences kinda stink. Fighting- or fairy-type moves do really well here, and should demolish his team handily enough. Mind that Zoroark is disguised as an Absol when it emerges... not that this will change your strategy a whole lot, since they're both straight dark-types. Absolite will Mega Evolve; beware its very high physical attacks.

Elite Four Phoebe
  • Banette, level 71
  • Chandelure, level 71
  • Drifblim, level 71
  • Dusknoir, level 71
  • Mismagius, level 71
  • Sableye, level 73
Reward: $11,680

Phoebe is much different from last time, and a fair bit more dangerous. Her pokemon are a fairly even split of speedy-but-brittle damage-dealers (Chandelure, Mismagius, Sableye) and hefty, slow bruisers who will absorb a lot of damage (Drifblim, Dusknoir). Ghost- and dark-type moves are ideal, particularly any that do special damage over physical. A dark-type will have the easiest time with this group. The key here is to not use your strongest moves to defeat Banette, as it will almost certainly use Grudge to drain the PP of said moves, thereby depriving you of your best ghost killers. Sableye is the Mega Evolver in this fight, but... it's just not that dangerous, y'know? Use fairy-type moves to wipe it with ease.

Elite Four Glacia
  • Abomasnow, level 72
  • Walrein, level 72
  • Froslass, level 72
  • Beartic, level 72
  • Vanilluxe, level 72
  • Glalie, level 74
Reward: $11,840

Glacia is stronger, but her team - Walrein aside - still suffers from a deplorable weakness to special fire-type moves. A single fire-type pokemon (or something that can use fire-type moves, like, say, a speedy dragon-type with Flamethrower) can quite easily sweep five-sixths of her team, and so long as you have an electric- or fighting-type to take out Walrein, you're set. (You can also use grass-type, but that's risky.) A fighting-type can also sweep much of the team, but you'll need an alternative for Froslass snce it's part ghost-type. Glalie is the Mega Evolver this time around, and it gets a great deal stronger, but it's still so frail. One hit from a speedy pokemon can usually wipe it easily.

Elite Four Drake
  • Altaria, level 73
  • Dragalge, level 73
  • Kingdra, level 73
  • Flygon, level 73
  • Haxorus, level 73
  • Salamence, level 75
Reward: $12,000

Drake doesn't change things up too much. He still has a lot of monstrous, hard-hitting dragons that fail pretty harshly against fairy-types. Sending out fellow dragon-types is pretty risky, but it's not too bad if you have the advantage in speed. None of his pokemon are amazingly bulky, so one-hit kills aren't out of the question. Ice also remains a powerful alternative if you don't want to risk Dragaelgae poisoning your fairy-types, though ice won't hurt Dragaelgae itself as much as you might like. Salamence receives the Mega Evolution this time, giving it some substantial boosts but not making it any less vulnerable to ice-type moves.

Champion Steven
  • Skarmory, level 77
  • Aggron, level 77
  • Aerodactyl, level 77
  • Carbink, level 77
  • Claydol, level 77
  • Metagross, level 79
Reward: $15,800, Metagrossite

Steven's battle may have changed the least of the five end game trainers, though he's still probably the hardest. Water-type moves like Surf are more useful this time around, thanks to Aerodactyl and Carbink, but fire-type moves are still quite handy for taking down Skarmory and Metagross. Metagross remains the Mega Evolver, and it's just plain stronger than before, albeit pretty much the same otherwise.

Defeat the Elite Four a second time and this will happen and, back in Littleroot, Professor Birch will have another fleeing hissy fit after you speak to your mother. This time you can choose between the Sinnoh starters: Turtwig, Chimchar, or Piplup.