It would be reasonable to have the substance unlock the latent magical potential in a person, say by flooding that force which connects them to the realm. For someone who is not born into this, one can imagine this alchemical compound can have profound effects, say extreme as [i]burning away parts of the soul itself[/i]. It withers the spirit, heart, mind and body. It is too much for the average person to maintain. Despite this, you can imagine the wealthy or elite might be drawn to that taste of power the envy, after all they are the elite - why should mundane folk be the only one allowed such power and just because they were fortunate enough to be born with it?

Understandably so such a substitute for real power, be it inborn or studied, would be rare and costly, but as with many forms of power or potential, it is an attractive option. While it might eat away at a person the addiction is powerful. A [i]little[/i] bit more would not hurt too much would it?

If anything I imagine the substance to be a powerful psychic stimulant, awakening the powers of the mind to tap into magic. Of course psionics do this, but those are gifts discovered by a select few. Something rarer than wizardry, witchcraft or sorcery. Even more poorly understood and far more unpredictable.

It might cause episodes of mania just by itself or awaken those urges.