In the original film, there seems to mainly be a transfer of power. In Highlander III: The Sorcerer, it is indicated that some knowledge might also transfer from a dead immortal to their killer. This same film, and certain episodes of the TV series, indicate that rare immortals may also have other seemingly supernatural powers, such as sorcery or clairvoyance. It may be that these are connected to their unique Quickening energy or that they may be unrelated powers that the person was born with, since Duncan MacLeod also encounters a human with clairvoyance who is completely mortal. In the anime Highlander: The Search for Vengeance, immortals can use their Quickening energy to attain increased strength and speed.