Where the medieval European unicorn is a creature defined chiefly by its gentleness and its capture only by a virgin, the karkadann of Persian and wider Middle Eastern legend is defined by the opposite temperament entirely: a large, heavily built, deliberately aggressive beast, roughly the bulk of an ox or a small elephant, that actively seeks out and fights other large animals rather than fleeing them. Its single great horn, mounted on the forehead, was described as strong and sharp enough to gore an elephant outright, and several tellings hold that elephants and other large beasts of the region genuinely feared and avoided it, a reputation for raw combat power the gentler unicorn legend never carried in anything like the same degree.
Alongside its violence, the karkadann's horn carried a second, entirely different property in the tradition: the power to detect poison, sweating or otherwise reacting when brought near a poisoned substance, or, in some tellings, to neutralize poison outright when a drinking vessel was fashioned from it. That property became one of the most durable pieces of the whole legend, surviving the beast's own gradual fading from serious natural-history writing and passing, through centuries of Persian, Arabic and eventually European compilers and translators moving material between traditions, into the poison-detecting unicorn horn of later medieval and early modern European lore, by which point the specific, violent karkadann that had originally carried the property had been largely replaced in popular memory by its gentler European cousin.