That night, as moonlight shone on Hogwarts Castle.
Something big was happening by the Black Lake.
An invisible magical force had parted the lake down the middle.
The water had been pushed to either side, forming two transparent walls dozens of meters high.
The lakebed lay exposed, turning into a vast, deep pit without a single drop of water.
A patch of water remained in the pit's northwest corner, where the Giant Squid lived. The water there was very calm, clearly under a soothing charm.
On the dry lakebed, a group of people worked in an orderly fashion.
Remus Lupin stood on a tall rock, directing them.
They were Silvermane Academy's first graduating class, all capable werewolves.
"Section B, lower the Siren's Voice rune frequency another five points! We're trying to guide people, not drive them mad with noise!"
Lupin's voice carried across the entire construction site through Sonorus.
Wearing waterproof work clothes bearing the Marauders Power Company logo, they moved deftly as they carefully installed light-refracting crystals designed by the Weasley Twins onto their bases.
At the other end of the site, Sirius Black, wearing the same work clothes, which he had altered to look very stylish, was arguing with Professor Flitwick.
"No, Filius! The magical power output of the heavy-water vortex needs to go up by at least another twenty percent!"
Sirius waved his arms, keeping his irritation in check.
"The merpeople patrol destroyed two of our bases last night. They're warning us. Unless we show them what we're capable of, this will never end, and the whole project will have to shut down."
Professor Flitwick jumped down from a stack of crates in anger and said shrilly:
"Show them what we're capable of? Sirius, that will only make things worse! Dumbledore reached an agreement with them before