The power to shape the world can also tear it apart. The power to summon spirits and gain allies can also conjure enemies and lead to your own destruction. And the power to fill objects with magic is also the ability to make them blow up in your face.
Shadowrunners learn about power the hard way - by being on the wrong end of it. That means they often gather it to them however they can, consequences be damned. Street Wyrd is a guide to all sorts of Awakened power, from spells to adept powers to new spirits to enhanced enchanting rules. It also gives runners the power to make their own spells to unleash on their enemies. Because runners know that the power you grab for yourself is the only thing that stays with you.
Street Wyrd is the core magic rulebook for Shadowrun: Sixth World.