Loki found out that he was not related to Thor, not related to Odin, not related to Frigga. He was adopted, left to die on the frozen wastes of Jotunheim, and taken into the family and he’s furious with Odin. And Frigga, his adoptive mother, is the only one who still cares. And Rene [Russo] is so delicate, and we always talked about this special bond that Loki and Frigga had, especially when Thor and Loki were children, that Thor was a chip off the old block. He was the quarterback. He was the son that Odin understood. And Loki was the student, an artist, someone who was more sensetive, more delicate. And Frigga understood that and nurtured that, and taught him all of her magic. And that bond was something that was a privilege to play. That here is this character, Loki, who is now condemned, imprisoned for eternity, to be forgotten, written out of history and haunted by his demons. The only person who still cares in the entire universe is his mother.
Thor: The Dark World Commentary (by Tom Hiddleston)