Ended up losing my Super Doubles streak at 18. Was a few days ago now, so can't remember all the details, but it did come down to the opponent's Gengar holding a Focus Sash, so literally lost by 1 HP.
With the run over I decided to leave the Battle Resort for a bit and return to finishing my Hoenn Dex. Only have the Regi's to go, so took the boat to Lilycove and then made my way to Pacifilog. I remembered from playing Emerald that you needed a Relincath and Wailord to catch them at some point, so added them to my team, before heading off into the currents. Took a few goes, (soared back to Pacifilog every-time it went wrong), but was able to get to an interesting looking dive spot soon enough. Dove down with Kyogre, and sure enough I soon came to the Sealed Chamber. Braille translation in hand, I set about solving the puzzles inside. Once completed I was informed that some doors far away had opened up, so left the Sealed Chamber and went looking for those.
I knew from earlier explorations of Hoenn that one was in the desert, so surfed the currents back to Slateport and then traveled up to the desert area via Mauville. Bought Metagross into my team for Hold Back and Breloom for its status effects, leaving Relincath and Wailord behind now they'd don their job. Once at the desert I headed south, and sure enough the door to the ruins had opened up. Took me a few goes to get into the right spot to solve the puzzle, but once I had a second chamber opened up. Within it Regirock was waiting.
Didn't want to take any chances, so led with Mega Metagross and used Hold Back until Regirock was down to 1 HP. Then switched in Latias and paralyzed it with Thunder Wave. From then on it was just a case of throwing Ultra Balls at it until it went inside. Went through about 20 in the end, but was able to catch it.
With Regirock in the bag I returned to Mauville and prepared to go looking for the next opened ruin. Hadn't been to Fortree in a long time, and needed to visit the Secret Base Guild to get a new rank, so decided to look up there first. Before heading off I switched my team around to make it more legendary-hunting worthy. In reality it would have been fine how it was, but added to the role playing element a bit. Bought in Flamer, (my Charizard from FR) and shiny Mewtwo, (also from FR) in place of Manetric and Breloom, (who wasn't really needed because Latias has Thunder Wave).
Headed up Route 119, battling in a few Secret Bases as I went, to Fortree. Didn't come across any ruins though. Once at Fortree I visited the Secret Base Guild and got the bronze and silver rank for my Secret Base. Then left and headed down Route 120. On the way I noticed a rock with a door in it in the middle of a lake, so surfed over and went through the door into the Scorched Slab. There I met Flannery, who had come looking for a legendary Pokemon but didn't feel able to progress any further. She left, and I progress further into the Scorched Slab. During my descent I found a Charizardite Y, which I gave to Flamer so he could mega evolve. Upon reaching the bottom I found a very hot chamber with a Hoopa portal at the end. Obviously this wasn't a Regi, but seeing as I had my legendary-hunting party with me, thought this was a good a time as any to catch whatever was behind the portal. Stuck my hand in, and predictably enough given the surroundings Heatran popped out. Led with Flamer, who I mega evolved into Charizard Y. Again, played it safe using a few not very effective Wing Attacks, before switching to Metagross for Hold Back and then Latias for Thunder Wave. Latias got burned by one of Heatran's Lava Plumes, so switched to Mewtwo, who has Recover, to stall out the turns while I chucked Ultra Balls at it. Went in much easier than Regirock, must have only been 5 or 6.