In the story, Galen, an apprentice technomage, discovers a peculiarity in his spell language (the mental visualizations that he uses to control his internal tech). To make a long story short, he finds that using the most basic "term" (he visualizes his spells as equations) for spheres alone essentially creates a spherical pocket universe that swiftly shrinks and crushes its contents.
The dangerous parts are, one, it's the most basic equation in the series--a single term, not the potentially dozens it takes to cast other spells, making it easy for him to cast, and two, it's essentially addictive for him to cast--he experiences a rush, a "burning, racing energy", when he casts the spell, making it quite dangerous to be within a few miles of him.
So, here's my thought, a proposal for a new drain modifier for the table in Street Magic, pg 163:
Addictive: this modifier modifies part of a spell's Drain from "damaging" to a rush that borders on euphoria. Combat spells only, -2 Drain modifier, but the mage must make an Addiction test (Willpower+(Drain Attribute))(Spell Force/2) each time he casts the spell. Once the mage is addicted, he must succeed in a Willpower+(Drain Attribute) (3) test to voluntarily stop casting the spell if targets are still available.
It sort of goes without saying that, unless you trust your players incredibly well, this is for NPCs only.
Now, as for uses...
- Magical researcher gone awry... and berserk.
- A combat mage looking for that extra edge gets more than he bargained for.
- A mundane spell designer gives a new combat spell to a friend to test and now has to stop him.
- The runners 'jack some notes and old tablets from an Aztechnology research lab; the Azzies want them back (of course), but once the word gets out, every Awakened terrorist organization is going to want to get their hooks into it.