an enchantment that simply gives all your creatures lifelink wouldn't count), nor simply require you to pay life.
The aim of this contest is to make an enchantment that causes one or more players to either gain life, lose life or both but which does not do direct noncombat damage, nor rely on damage for the lifegain / lifeloss (e.g. Hot on the heels of Enchantment Contest #6 ( ).