Many adventurers have preturnatural advantages over their mundane counterparts. These are often minor circumstantial talents, impossible to quantify or even to identify as anything but luck. Yet, some adventurers display arcane knowledge or physical mutations so powerful or bizarre as to make them objects of study in their own right. Adventurers commonly refer to such amazing capabilities as “Knacks”.
Like a character's other Traits - from her skills to her allegiance to her Inspiration - Knacks are simply another component of who she is. They are not meant to replace cleverness and ingenuity, but to accentuate them when appropriate. So while Knacks can come in handy, a character should not rely overmuch on them to get her out of tight spots. It's worth noting that some Inspired have no Knacks at all.
For game purposes, Knacks are divided into three categories: heroic, psychic and dynamic. Knacks are only available to Inspired characters - mere mortals cannot hope to attain such gifts. An Inspired character's access to Knacks is based on the path to heroism (or villainy…) that she has chosen: Daredevils may purchase heroic Knacks, mesmerists can develop psychic knacks, and stalwarts gain dynamic Knacks.
All Knacks run on Inspiration. Heroic Knacks simply require that the character be Inspired, while many psychic and dynamic Knacks cost Inspiration to use. Use most of Knacks requires a roll; if this is the case, the Knack's individual rules describe the mechanics for that roll.
The same Knack can manifest in many different ways, depending on how an individual character sees herself. As far as the rules are concerned, a sorcerer who calls on the power of D'eedre and flings bolts of screaming green flame is doing the same thing as a highly discipline physicist who ignites flammable materials by exciting their molocules via the exertions of his own will. They're both using the Knack called Flame Cojuration. In fact, as far as the science of telleric energy is concerned, the two effects register identically - both give the same readings on a Z-wave image resonator. Still, to outside observers, each individual creates a wildly different effect. When describing a character's Knacks, remember that there are many paths to the same results. Pick one that fits the character's unique style.