JÓLASVEINAR
The Yule Lads, or Yulemen, (Icelandic: jólasveinarnir or jólasveinar) are figures from Icelandic folklore who in modern times have become the Icelandic version of Santa Claus. Their number has varied throughout the ages, but currently they are considered to be thirteen.
The Yule Lads originate from Icelandic folklore. Early on their numbers and depictions varied greatly depending on location, with each individual Lad ranging from mere pranksters to homicidal monsters who eat children.
The Yule Lads are traditionally said to be the sons of the mountain-dwelling trolls Grýla and Leppalúði. Additionally, the Yule Lads are often depicted with the Yuletide Cat, a giant ferocius cat that, according to folklore, eats children that don't receive new clothes in time for Christmas.
The Yule Lads were originally portrayed as being mischievous, or even criminal, pranksters that would steal from, or in other way harass the population (at the time mostly rural farmers). They all had descriptive names that conveyed their modus operandi.
In modern times the Yule Lads have been depicted as taking on a more benevolent role comparable to Santa Claus and other related figures and putting small gifts (or potatoes if the child has misbehaved) into shoes placed by children into their windows the last thirteen nights before Christmas Eve. They are occasionally depicted as wearing the costume traditionally worn by the American Santa Claus, but are otherwise generally shown wearing late medieval style Icelandic clothing.
The Yule lads are said to "come to town" during the last 13 nights before Christmas, each staying for two weeks before departing.

TRÖLL
Trolls are creatures in Icelandic folklore. Trolls are crude, although they said to be always true to their word. They will turn to stone if exposed to sunlight. According to Jacqueline Simpson, "Icelandic trolls are in most ways the direct descendants of the stupid, dangerous giants of Scandinavian myth, but differ from them in being generally solitary creatures, and in being so often associated with particular rocks and other landmarks."

HULDUFÓLK
Huldufólk (Icelandic hidden people from huldu- “pertaining to secrecy” and fólk “people”, “folk”) are elves in Icelandic folklore. Building projects in Iceland are sometimes altered to prevent damaging the rocks where they are believed to live. According to these Icelandic folk beliefs, one should never throw stones because of the possibility of hitting the huldufólk. Some Icelanders have also built tiny churches to convert elves to Christianity.
Hidden people often appear in the significant or prophetic dreams of Icelanders. They are usually described as wearing 19th-century Icelandic clothing,and are often described as wearing green.
President Ólafur Ragnar Grímsson has explained the existence of huldufólk tales by saying: "Icelanders are few in number, so in the old times we doubled our population with tales of elves and fairies.

Written by Óskar Þór