A layer of mist rose beside the Black Lake after the rain.
Dozens of pairs of feet had left footprints all over the muddy path.
Unlike last term's simple morning runs, today every student had rings around their wrists and ankles.
They were four silver-gray metal rings as thick as a thumb, engraved with intricate alchemical runes.
The Marauders Power Company logo was stamped inside the clasps.
The product was called the Adaptive Weighted Training Ring.
It automatically adjusted its weight according to the wearer's current stamina, growing lighter as they tired and immediately adding the weight back as their strength recovered.
It always kept you at the point where you "just wanted to die but couldn't."
"Who invented this thing?"
Ron knelt on one knee in the mud, panting hard, his red hair clumped together with sweat.
"I seriously suspect Fred and George were drinking Butterbeer when they designed this thing."
"The instruction manual calls it gentle, progressive muscle activation."
Hermione ran past him, her steps heavy but her rhythm unbroken.
She still held a small booklet with a Waterproofing Charm on it, turning the pages as she ran.
"But I noticed an interesting technical detail."
She lowered her voice.
"The underlying architecture of this rune circuit uses the same Magic-Sensing Protocol as Golden Skynet's home defense arrays."
"So this thing doesn't just build stamina, it also makes our bodies adapt to Skynet's magical frequency band?"
Harry caught up from behind.
His breathing was much steadier than either of his friends'.
After a whole summer of Douglas tormenting him with test papers and making him help Dudley lose weight, the results were finally showing.
"That's more or less it."
Hermione closed the booklet.
"Strategically speaking, this improves wizards' ability to survive in anti-spell zones.
When your wand is broken