After defeating the champion and Elite Four (which, by the way, took an extremely long time) and registering myself into the Hall of Fame, I immediately went to explore the Survival Area. When I arrived there, the first thing I did was, if I remember correctly, battle Barry. I managed to defeat him somehow, but his Pokémon were a lot stronger than ever before. His Staraptor's attacks were quite powerful; it was able to take out three - four of my Pokémon in an instant. I had a Metagross, though, which was able to take a few hits from it and strike back. I had a Snorlax, too. If I didn't have Metagross on my team, then I could've used that instead, and it would have been able to counter Staraptor without any worries. When I was done with Barry, I payed a little visit to Stark Mountain. There, I've met Buck. I had to help him search for the Magma Stone. After that, he introduced me to the Battleground--a place where many of the toughest Sinnoh region trainers hanged out, which was ran by his grandfather. I decided to go head-to-head with some of the trainers, and by winning, I was able to level-up my Pokémon quite a bit. (:
Eventually, I learned that if you revisit Stark Mountain, you'd be able to capture Heatran... and so I did! I was able to catch Heatran, but it took me more than a hundred Dusk Balls. I had it down to its lowest possible health, and paralyzed it as well--no luck. It would still break out of the Poké Ball pretty easily. Thank god that I had it captured at some point, though. If it ran out of moves and used Struggle, then I would've been required to go through the whole process all over again. Other than those things, I've done a lot of other stuff. But right now, I just can't seem to recall them, precisely. I think I tried completing the PokéDex, but I just couldn't get it done at the end. It was too time-consuming, and my motivation for it simply wasn't there anymore. D: