When not stuffing their faces eating they are out terrorizing women in the middle of the night with their irresistible good-looks, and manly mannerisms, seducing them in their dreams to preform sexual relations, unbeknown to the women. They're able to last on love, draining humans of it, if food is scarce.
He usually works alone, venturing out on his own after reaching sexual maturity. If you listen late at night you can sometimes hear them playing their music, they are very gifted, very charming and possess singing voices to rival Willy Nelson.
The thing about a Gancanagh is he can fool you through all your five senses, making themselves invisible just when you think they've gone, you turn over and there he is again. You just can't get rid of him until he gets what he has come for, SEX!
They have a fear of elevators, cars, planes and trains anything that surrounds them in metal being deathly allergic to iron.
Gancanagh secretes a highly addictive ingredient that makes humans irresistible to them. He's a sweet talker. Woman and sometimes men will scammer to have a chance or another go with him. The victim eventually tires after repeated sexual assaults, sometimes lasting years, and usually die wasting away. Gancanagh are relentless when it comes to sex. Also, it's not unusual for any of Gancanagh's victims to die of a broken heart. Apparently, he's really good. I've heard of women fight to the death with other women over him.
You can't kill one. They cannot die a normal natural death, they keep ageing to be about 600 years old, then after that stop ageing and live forever, never siring any children of their own, if one is accidentally born, the child automatically turns into a Gancanagh.
If you ever meet one, you're in for a rocky road ahead. Bad luck will soon follow.