Some killers report a 'rush' as their victim dies in their presence and I often wonder if mass murderers, whether one person (Daumer, Gates, etc.) taking out a series of victims, or soldiers and politicians (Hitler, Pol Pot, etc.) who order mass killings, might gain some power which they could redirect to alter their reality and give them more power and control over others.
In the instances below, the purpose is for healing and rejuvenation of the older by sapping/absorbing the life/vital force of the younger.
"We know that it is healthy to live in an atmosphere filled with the restorative emanations given out by bodies young and full of vigor. We see in the third book of Kings that David lay with comely damsels to warm him and to give him a little strength.
According to Galen and others, Greek doctors had long recognized in the treatment of sundry consumptions, the advantage of making the patients take nourishment from the breast of young, healthy nurses; and experience had taught them that "the effect is not the same when the milk is given after being caught in a vessel."
Cappivaccius saved the heir of a great house in Italy fallen into marasmus (marasmus n. A progressive wasting of the body, occurring chiefly in young children and associated with insufficient intake or malabsorption of food.), by making him lie betwixt two vigorous young girls.
Forestus tells how a young Pole was cured of marasmus by spending the days and nights with a nurse of twenty years; and the effect of the remedy was as prompt as it was successful.
Finally, to bring this subject to an end, Boerhaave used to tell his disciples of having seen a German prince cured by this means, employed in the same way which had succeeded so well for Cappivaccius. There is not a housewife but knows that it is not good for a child to sleep with an aged person, though the latter enjoy perfect health.
If we seek for such a general instance of the influence of one human being on another as may seem like that mutual loss and gain and interchange of vital force, which is the principal wonder in mesmerism, we have only to look at the effects produced when young people sleep with old.
Since the days of King David it has been known that the latter are strengthened at the expense of the former... I was acquainted with an infirm old lady, who was so aware of the benefit that she derived from sleeping with young people, that, with a sort of horrid vampirism, she always obliged her maids to share her bed, thus successively destroying the health of several attendants.
Even among animals it has been found that the young cannot be too closely associated with the old without suffering detriment. Young horses standing in a stable with old ones become less healthy.
The celebrated German physiologist, Hufeland, has remarked the longevity of school masters, and he attributes it to their living so constantly amidst the healthy emanations of young persons."