The Prime Acid, known also as oil of blending is a thin superfluidic liquid that does far more than eat away base substance as other acids do. The strongest of acids dissolves the very notion of individuality itself, the fundamental distinction between objects.
If spilled on a hand one would hardly notice any immediate difference. There would be no searing pain or sizzling of flesh. Yet something more insidious has taken place, the member now divorced from notions of unique existence. Should that member reach out to grasp at a sword hilt the two would appear to blend. More exactly, according to the arcane sciences which have created the Prime Acid, there would no longer be hand and sword; rather a single thing which incorporates both.
With this potion bodies can be blended, incompatible essences merged, and new hybrids created of anything which it touches. No container can truly hold such a virulent substances, rather it must be kept continually in suspension through some means. One of its creators discovered this in an unfortunate accident, as Harlan the Alchemist became the Amalgam.