What if Knacks were the Lunars' natural powers designed to supplement their inherent shapeshifting ability. When the Silver Pact created moonsilver tattoos to protect themselves against the degenerate effects of the Great Curse they started using Charms outside of Martial Arts and Sorcery to emulate these effects. Many believe that this is when Luna turned her sight from her Children for refusing the gifts she gave them. Those who refuse tattooing believe this fervently, believing their rejection of their transformation into animal form was a clear rejection of Luna's nature of her Chosen.
When the Primordials levelled the Great Curse on the Lunars they condemned them to be the animals they'd become. As they grew older their bodies became an amalgamation of their human form and their spirit shape until it was recognisable as neither. This was the Lunar's new and only True Form. They were the first Beastmen.
Expand Lunar Knacks across Attributes so they are a full family of powers. Charms may be prefereable since they were invented rather than discovered but they are not the true powers of the Lunars.
All Knack are shapeshifting effects; they might change their skin into another colour or a different type of tissue altogether in Hundred Skins Hunter or become as lithe and sensuous as a stalking cat in Silent Jaguar Steps. These powers aren't just magic effects like Charms, they actually change an aspect of the Lunar's physical form. A character using Silent Jaguar Steps doesn't just use Essence to surpress the sound of his footfalls as a Night Caste might, he walks with such stealth and gracefulness that his movements make no noise.
Even at night in the darkest forest he makes no sound.
But the price exacted was terrible, a Lunar with tattoos was incapable of shapeshifting.
The Lunars feared such a condemnation of their animal nature and what consequences it might provoke from Luna. They also darkly warned about the consequences of using moonsilver for something against it's natural purpose. Craftsmen speculate that it was this perversion that caused Luna to withdraw her favour from them.
Understanding of their new family of powers highlighted the difference between them: Charms imitate, Knacks alter. A Solar would use Charms to see and interract with dematerialised spirits. A Lunar would assume the form of something that could do that. This is the great versitility of Knacks. Lunars who use Knacks can also learn Charms, they appear to suffer no approbrium for doing so, it's unlikely Luna even knows they do, but find them unnecessary compared to Knacks. Knacks can't make a Luanr do everything a Solar can, but they're not supposed to. A Solar can't turn themselves into a Behemoth at a moment's notice.
Physical Knacks often work obviously, changing a visible aspect of their nature. Other work by inward focus.
