Shadar-kai lurk in the gloom. They are maddened by pain, driven by desire, and linked perversely to death and nothingness. As a people, they aren't evil, but their morals lack a stripe of humanity more decent folk expect. The shadar-kai culture is a sometimes-cruel meritocracy consisting of contests of wit, skill, and bloody combat. The shadar-kai play these games among their own kind and with other creatures, seeking peak experience above all other goals.
For lighter, more purely story-based fun, check out another article I wrote called the Zhent Headless Horseman, also recently published in Dragon in Realmslore. It provides a seed for any number of interesting adventures, but as I intimated, is also a tale you might hear around a tavern hearth.