It arrives near the moment of death and steals spirit from the body.
(From Bulbapedia) Lampent has a clear, spherical head containing a bluish purple flame and oval, yellow eyes. On top of its head is a black covering, which resembles a lampshade, with a pointed spike on top. Underneath its head is a small, black body with a pointed spike at the bottom. Extending from its body are two long, wavy arms with no fingers. It floats through the air to move.
Lampent can sense when someone is about to die, whom it visits and steals the spirit from the person's body. Though most often found in deep forests, it wanders through cities and hangs around near hospitals to absorb the spirits of the fallen. It uses the spirits it has absorbed to fuel its fire. On occasion, it has been known to work with Litwick to lead people to the Ghost World while stealing life energy.
(From Bulbapedia) Lampent is a combination of Hitodama (a blue, black, or purple-fire associated with ghosts and yōkai, equivalent to the western will-o'-the-wisp) and an oil street lamp.
(From Bulbapedia) LLampent may be a combination of lamp and lambent (softly glowing, with connotations of otherworldliness) or repent (to feel sorrow or regret). It may also refer to lament (to feel sorrow or grief), a corruption of rampant (to be violent), bent (referring to Lampent's bent arms), or entity (based on Lampent's supernatural origins). It may also involve pent (to be trapped).