Arya snapped out of it and gave orders to the troops standing in the room. "Get everything out of those rooms, send the plates to the maesters, and send the precious stuff to the vault. Do not touch the plate on the wall in the throne room, or the capstone will open, and I want guards there in case it is opened somehow. I want every room searched and searched again, every wall for hollow places, drag everything from that place, and we will study it. And dispose of all those Deep One corpses." With that, she moved away towards her apartments with Thomas and Jon Snow in tow.
As the cleanup crew was toting all the Deep One corpses away, they passed Drogon's area, and the dragon mewed towards the corpses. One of them ran and asked Jon Snow if the dragon could have them, and he agreed. More than two dozen corpses were dumped at Drogon's feet, and he feasted on them, making happy sounds...well, happy for a dragon anyway.
Three more hidden doors were found during the searching, but no one could open them no matter how they tried. Stone-kin experts marveled at the oily black stone and hammered away at it, trying to break some off. All their efforts got them not one piece of that stone. They did all manner of testing on it to no result; it mystified their experts and tested their resolve, even as they tried to scratch it. Tormund sold his mithril bolts to the stone-kin and gave half to Brienne for her sacrifice in the rooms, but he told others it was her bride price. The other half went to the town's vault. Arya awarded him a house in town, a new one that was being built in the new north section. She told him under her breath that it was for Brienne and him to set up house, and his smile went from ear to ear. The two of them were married before spring, and they moved into the house before it was even finished. The wedding was the biggest event of the winter, and Brienne made bank on all the bride gifts. She used some of the wealth to commission Gendry and Thomas to make her a leg prosthetic.
The wedding slightly overshadowed the other large event, the funeral of Siora.
A huge amount of tree-kin made their way to the city for it, and she was hailed as a hero to Westeros. Even Bran came to honor her and ensure she was buried with full honors, then attended Brienne's marriage. He toured the portal rooms and studied all the finds that had been made. Arya split the returns from the stones and metals with him, and he took them back to King's Landing with him when he left. Before he left, he commissioned a new maester building in the new north area of town, the biggest one anywhere but in King's Landing. He said it was for studying the portal rooms and the rune plates they had found. When spring came around, more than a hundred maesters and their apprentices came to be a part of it. The maesters pestered Tormund until he sent out messages all over north of the wall for any wildlings with the skills who wanted to study runes. 20 of them showed up in the spring and stunned the maesters with their skill and knowledge. Brienne and Tormund paid them 100 gold pieces each out of their personal funds... or most of them wouldn't have come.
As the study of the plates got more and more intense, some of the maesters conjectured that part of it was pure gibberish. Something about combining sound and light to mold the black stone, the stone-kin began to study the runes too, trying to make heads or tails of it. Then one of the searchers in the portal room discovered a small wall panel by running his hand all over the walls. When the panel was opened, three small, very complex devices were found inside. Two of them had strange gemstones in them, and it took 6 tree-kin scholars two months to make one work. It melted the stone tabletop it was pointed at. The stone-kin went ballistic when that happened; they had to be taught how it worked, how to make more, and how to use them. They tried to buy one but ended up funding the maester's work for a year with the understanding they would be kept in the know and allowed to use one. They weren't happy, but they were grinning when they agreed to the terms.
Then one of the youngest wildlings studying there went out one night and got blind drunk. He staggered back to the maesters' building at dawn and collapsed in his bed. He had a vision, or a dream, while he slept it off, and he related that vision after he awoke. One of the three devices they found was a small square box, and he said in his dream the square box was to be placed in the hottest fire. He didn't know what happened after that, just that it needed to go into a fire. The maesters all opposed any such treatment of a rare artifact, but the stone-kin helped him snatch it and started carrying it to their forge. Three maesters in their nightshirts were following the group, screaming nine kinds of hellish threats at the young wildling and the stone-kin. Thomas and Gendry at their forge heard this commotion and followed the group.