Dhar, more commonly known as Dark or Black Magic requires no skill or time to use. It is easy access to spells equal to that wielded by Elven Archmages; in exchange, the costs of it are equally great, oftentimes causing mutation, damage to reality, and corrupting & twisting the environment. The reason for these dangerous side effects to the caster and their surroundings is the wasteful and careless way in which Dhar must be casted. Indeed, the way to cast with Dhar is similarly destructive, demanding only incredible amounts of willpower and simply crushing them together.
There are 2 kinds of Dhar, Dhar and True Dhar. Dhar is using all the Winds of Magic for maximum effect in an unbalanced manner. True Dhar is made when all eight winds merge together so thoroughly that maintain an individual identity, stagnating in a metaphysical sense.
Where the Dhar used by regular wizards could perhaps be consider not evil; True Dhar is bent almost entirely towards dominating and deconstructing the physical world. True Dhar is just as difficult as Qhaysh to wield, but also carries a much higher risk of consuming the being who casts with it. True Dhar must be wrestled into shape, requiring a will and mind of such strength and narcissistic self-confidence that only the most mad humans could ever hope to have. And even the most stable of people will become absolutely self-obsessed in a relatively short amount of time when exposed to True Dhar.
This power makes you a natural talent for working with True Dhar, granting you the megalomaniacal self-confidence and nigh-absolute strength of will and mind to wield it. It also grants you enough skill to be on par with an average Supreme Sorceress; however even your average Supreme Sorceress is capable of turning the tide of entire battlefields and decimating large portions of enemy armies.
You do not need to purchase this to wield Dhar, this merely grants you the experience and skill required to do so somewhat safely.