DESTROYING A LEPRECHAUN:
1 - A Leprechaun is in fact mortal and can be killed like anyone else, however tricking him into being killed is nearly impossible.
2 - Wrought iron will burn a Leprechaun (i.e. If you want to hold a Leprechaun, use wrought iron "cage"😉.
3 - Leprechauns love liquor. They can be enticed by the alcohol and will get drunk. However, the Leprechaun's metabolism is magical. They can consume much more alcohol than mortals and they can sober up much faster than a mortal.
MARRIAGE: Leprechauns can only marry every thousand years on their thousandth birthday, if they catch the mortal lass of their choice and have her sneeze three times without anyone saying "God bless you." At that point, magically, a ring appears on her finger and a shackle around her neck.