Snow fell without a trace, but geese left their cries behind.
Every use of magic left clues. Perhaps space developed an unusual fold, perhaps a Magic Potion left a distinctive scent, or perhaps a severed dimensional thread cast a Mirage Shadow into reality.
The clearest sign of all, however, was the Magic Power left behind after a spell was cast.
Just as firing a gun left traces of gunpowder, a wizard's use of Magic Power left a little residual Spiritual Essence on the wizard or in the surrounding air. Many experienced hunting teams knew how to measure it during hunting competitions and use the results to assess the terrain. Organizations such as the Trident Sword Organization also measured magical residue in their routine investigations.
First University students trained to detect magical residue in their first-year practical classes. As an outstanding student of Jiu You Academy, Jiang Yu could tell at a glance, even without an alchemical instrument, that the gray-robed witch carried traces of very recent magic.
And the residue left by different spells varied in subtle ways.
The residue on that witch happened to match what Jiu You Academy students knew best: the traces left by a Binding Spell. The Binding Spell was a "standard incantation" certified by the Wizard Alliance.
Standard incantations produced substantial magical effects and required both Magic Power and considerable training to cast. They were entirely different from Innate Magic such as a Vampire's "bloodthirsty recovery," a Werewolf's "moonlit frenzy," or a foxfolk's "natural allure." Nor were they anything like the little flames Tricksters conjured with a snap of their fingers, the bouquets they pulled from hats, or the suits they changed on playing cards.
The Wizard Codex classified Tricksters as wizards, but their sensitivity to Magic Power was so low that they could use