Idea credit to Darth Krande.
It was winter when Albus next came to visit. Gellert was curled in the chair that had yet to disappear when the wizard stormed in and started ranting about foolish committees and weak willed boards. Gellert didn't understand half of it but he smiled all the same. Albus was just as emotional as usual, sure age and experience had tempered his tendency to rush into things but there was still hope for manipulating him. Albus' presence here alone meant that he had been somewhat successful in convincing the other wizard that he was harmless and that their relationship was salvageable. The more Albus trusted him, the greater the chance that Gellert could slip through his fingers.
The dark wizard focused on the ranting, trying to figure out exactly why such a respected wizard had appeared this late at night when he should have been at his school. Eventually, among the torrent of English he managed to pick out something about a chamber and the board of governors.
With the true reason for this disturbance still a mystery, Gellert managed to interrupt the wizard after several minutes and Albus finally fell silent.
'It appears that I missed the beginning of this story, Albus.' Gellert drawled, forcing his frozen limbs to uncurl so that he was lounging casually rather than desperately preserving warmth. The visitor turned to him and frustratedly explained exactly what had happened. Of course, Dumbledore was easily assuming that these attacks had something to do with Voldemort and he'd come to verify that Gellert still had the stone kept safely in his cell.
The dark wizard confirmed, but made no move to leave the chair, unwilling to give up the only warmth that he had managed to retain until he could shovel out the snow in the morning. Albus seemed content with just a verbal confirmation at least, and he conjured himself another chair and settled down as if to chat.
Gellert didn't complain when the other produced another packet of sweets, this time a large bag of Dominostein. He poured them both a dark coffee and seemingly noticing for the first time how cold it was, conjured a thick blanket each.
'So how have you been?' The light wizard asked, avoiding the obvious hippogriff in the room. Dumbledore looked over the diagrams carved into the wall with obvious interest, even though Gellert knew that unless the other wizard had finally deigned to learn German, he wouldn't understand them.
'Bored.' Gellert finally decided to say. It was a neutral enough answer, unlikely to give any hint as to how he'd been working on his magic and hopefully enough of an answer that Albus wouldn't pursue it any further. 'I assume you're kept busy as headmaster?' It really was frustrating how his accent had returned after so many years of trying to iron it out.
He listened as Albus talked animatedly about his research on dragon's blood. It was during this that Gellert discovered that his name was also on a chocolate frog card, which Albus promised to send him when he next had a chance. Even though Gellert really had no interest in dragon's blood and its uses in household charms, he was happy to listen to the other's ideas and thoughts if it meant hearing him speak.
Albus was happy to talk for several hours before he finally decided to press Gellert on how he'd occupied his time. And so the dark wizard showed him how the rocks on the other side of the valley looked like a ship and explained how if the moon was just right it would reflect on the ceiling like a witch on a broomstick. He explained some of the drawings on the walls, not bothering to hide that the older ones were meant to help break the warding. Albus would be suspicious if he hadn't at least tried to break out. Of course he made sure to inject just the right amount of humour as he described his various attempts.
Albus laughed a lot and seemed to believe him until eventually Gellert ran out of things to say and the two wizards settled down on their chairs with a brandy. Albus was quick to fall asleep in his chair, sprawled uncomfortably with his beard slung over his shoulder. Gellert remained awake, watching the moon set through the window. He considered stealing Albus' wand, fighting internally over the desire to be free and knowledge that Albus had almost certainly warded his person to stop such an occurrence.
The familiar handle protruded out of the sleeping wizard's sleeve and it sung to the darkness within Gellert. Of course, the elder wand was not built to be a light wizard's wand. It craved the destruction of dark magic almost as much as Gellert did. He knew that it would take very little for the wand to change ownership but he would only get one chance.
Now was not it.
Albus seemed pleased and surprised when he woke to find Gellert already awake, confirming his theory that leaving the wand "defenseless" had been a test. One that he'd passed with flying colours.
He'd already eaten his daily bowl of cold porridge, improved by the remaining Dominostein and a heating charm and shoveled most of the snow out of the window. It was rather satisfying to see how soft his friend had become in his old age. Years of safety and comfort meant that he slept in until late morning despite someone nearby being less than quiet.
It was a weakness Gellert would be happy to exploit as his imprisonment had kept him harshly conditioned.
That being said, he still wasn't planning to share his meager breakfast just for the purpose of gaining an ally. Albus however seemed to have no such reservations with a seemingly inexhaustible supply of tea and coffee in his cloak and pulled two rosy apples from somewhere about his person
This time, when the other wizard left it was with a long, measuring look that Gellert pretended not to notice.