According with the Mapuche's "mythology" or should I say Mapuche's knowledge:
The Huecufu (or Wekufe) is an almost disembodied "evil" entity that prowl the south... Andean (The Andes) fields and roads, "It" brings plague and death.
In other words the Wekufe disturbs the earth balance and are the only (?) entity without a soul in the land.
( they are like the shallowness from the Neverending Story)
They says that many Wekufes can be controled and summoned by the "Calcus/Kalkus" (Mapuche sorcerers) and use them in many evil purposes...like to sick people and animals for example.
to meet the Calcu :>
Pfff!!! there is so many history, but my english, sadly, is very poor, so I'll be brief.
To be safe from the Wekufes and Calcus, the Mapuches performs the "Machitún" and "Nguillatún" ceremonys by the local "Machi" (She is "like" a priestess)
Ok, that is it!
Pardon for my bad english but I do my best >_<