Not much is known about Erik Selvig's history except that he is from Copenhagen, and is a scientist and a doctor and became employed by S.H.I.E.L.D.
Erik Selvig was created for the Marvel Cinematic Universe, and appears in several films before starring in a movie tie-in comic. His first appearance in the Main Marvel Universe was in Avengers Standoff: Welcome to Pleasant Hill issue 1 by Nick Spencer and Mark Bagley.
Major Story Arcs
Erik Selvig works as an doctor and agent for S.H.I.E.L.D.. He was stationed in Pleasant Hill. During his time in Pleasant Hill, he was part of the crew that witnessed the formation of Cobic, a Cosmic Cube turned sentient and manifested itself as a young girl with enormous powers.
Erik was tasked by SHIELD with bringing up the little girl, learning her of what is right and what is wrong. It was however when Cobic met the Red Skull and believed that he was a hero, that she started changing reality. Doctor Erik Selvig was one of the first to be transformed into a slave of the Red Skull.
Erik Selvig is played by Stellan Skarsgard in each of his appearances and is a scientist whom works with Jane Foster and Darcy Lewis and was one of the first mortals to meet the Asgardian God Thor. Erik and his colleagues Jane and Darcy helped Thor during his struggle against Thor's evil half-brother Loki. A deleted line from the first Thor film suggests that Selvig is friends with Henry Pym.
The Avengers (2012)
During Loki's siege on Earth which caused the Avengers to be assembled, Erik was possessed by Loki to do his bidings. Eventually, Loki was defeated and Erik was brought back to his right state of mind.
Thor: The Dark World (2013)
Although Erik had been freed of Loki's possession in The Avengers, the months after, it was notable he still had to come to terms with the fact of having been possessed.
Avengers: Age of Ultron (2015)
Erik is once more part of the surrounding cast of the Avengers. Seemingly back in good spirits, Erik is seen teaching a class in University when he is contacted by Thor to help locate an ancient well for him.