The ward construction began in the second week of March, in the Room of Requirements, in the evenings after the training sessions had finished and the others had gone.
He and Hermione worked from opposite ends of the same problem.
She had the theoretical framework for magical law — the specific question of what a ward was legally permitted to do to an uninvited party, which turned out to be considerably more complex than the standard approach of simply building the most effective ward possible and asking questions afterward. She had been building this framework since the Muggle-born rights bibliography in third year and had, by March of fourth year, a working understanding of the intersection between magical construction and wizarding legal precedent that Ron suspected was better than most practicing ward-setters possessed.
He had the runic architecture. The Northumbrian transitional corpus work from the autumn had given him a framework for runic synthesis — the way different systems could be combined deliberately rather than accidentally — and he had been applying it since January to the specific problem of constructing wards that could be set quickly, held reliably, and dismantled cleanly.
The first ward he built in the Room was a basic exclusionary field — keyed to intent rather than identity, which meant it responded to hostile magical intent rather than to a specific person's presence. The advantage was that it required no prior knowledge of the people it was designed to exclude. The disadvantage was that defining hostile intent with sufficient precision to avoid false positives required careful runic specification.
'The intent definition is too broad,' Hermione said, on the third evening, looking at his runic sequence on the parchment. 'You've written it so that anyone carrying a defensive curse would trigger it. That includes most of the Order, if there is an Order, and certainly includes us.'
He looked at the sequence. She was correct. 'The distinction is between intent to harm and intent to defend,' he said. 'The rune for intent doesn't have a standard sub-variant for directionality.'
'I know,' she said. 'Which means you need to create one.'
He looked at her.
'Directional intent,' she said. 'A rune that encodes not just the presence of an intent but its target vector. If the hostile magic is directed outward toward someone in the protected space, it triggers. If it's held defensively with no current target, it doesn't.' She paused. 'The Northumbrian transitional corpus has three examples of directional runic modifiers. I found them last week.'
He stared at her. 'You've been reading the transitional corpus.'
'You gave me Babbling's notes in October,' she said, with the patient quality of someone who had been waiting for this conversation. 'I've been working through them since January. The directional modifiers are in section four of the Hexham inscription set. I was going to mention it but I wanted to be sure first.'
He looked at her across the table in the Room of Requirements on a Wednesday evening in March, and thought: this is who she is. She found the thing I needed in a text I gave her months ago and confirmed it before she said anything. She has been doing this since the first day I met her.
'Show me the section,' he said.
She opened the folder she had been working from and turned to page forty-three, and they worked until eleven o'clock without speaking much, which was the best kind of working.
The ward breaker came from a different direction — not runic construction but runic reading at speed, the specific skill of diagnosing a ward's architecture quickly enough to identify its keystone before it identified the person doing the diagnosing. He had been building this since the ward work in January with the group, and by March it was becoming fast enough to be reliable. He taught Hermione the diagnostic sequence over two sessions and she reached reliable speed in four days, which was characteristic.
The magic dampening attack was the hardest.
It was not a ward and not a curse — it was a field effect, designed to reduce the available magical bandwidth in a defined space temporarily. The theory was straightforward: all magic operated through a medium that could be disrupted, the way radio signals could be disrupted by interference. Creating the interference required a specific runic construct that he had been building toward since the Northumbrian synthesis work and which finally came together in the third week of March in the Room of Requirements at half past nine on a Tuesday night, when the construct he had been refining for six weeks finally settled into a coherent whole and held without collapsing.
The Room went slightly flat when it activated. Not dramatically — not the sudden silence of a total magical null, but the specific quality of a space where magic required more effort than it should. Hermione's wand, when she tried a simple Lumos, produced the light after a half-second delay it should not have had.
'That's it,' she said.
'Yes,' he said.
She looked at the space around them. 'How long does it hold?'
'Currently about ninety seconds,' he said. 'I want to get it to three minutes. And I want to reduce the cast time — right now it takes eight seconds to deploy, which is too long in a field situation.'
'What's your target?'
'Three seconds,' he said. 'And three minutes duration.'
She looked at him. 'That's a significant gap.'
'I have until June,' he said.
She accepted this, because she understood what June meant, and what the third task was, and what came after it if they could not prevent it. She turned back to the parchment and said: 'The Hexham directional modifier might be adaptable for the cast sequence. The compression technique it uses for the directional encoding — '
'Show me,' he said.
She turned to the relevant page. They worked until midnight.