Algrim/Kurse (played by Adewale Akinnuoye-Agbaje) is able to transform iron into Elven weapons in the film. In the comics, Malekith, Algrim and the dark elves (including notable characters Wormwood and Grendell) have a weakness to iron, along with another character from Marvel’s take on Arthurian legend (see: Stonehenge).
Props Master Barry Gibbs:
“Malekith does pick up other realm weapons and use it, uses it for one realm and then discards it. He doesn’t need to be carrying it around. And whereas Algrim being his captain or second in command, there’s only one element where he picks up some iron weapons and turns them into Elven weapons, so he curses them, so that happens in the movie as well.”
Out of context we’re not quite sure what this means but iron plays an interesting role in Marvel Comics in relation to the Dark Elves, and “magic” seems to play a large role in the film with the “fabric of the universe” falling apart being a big plot point. We know from the trailers Malekith has (or acquires) special abilities – holding Jane Foster in the air with telekinesis and creating a red vortex around himself in London – and in the comics Frigga (Thor’s mom) teaches Odin sorcery.
Disney and Marvel’s official description of Kurse may hint at Kurse gaining a special power (is cursing iron it?) after his transformation:
Algrim/Kurse is Malekith’s trusted and loyal lieutenant. He fought at Malekith’s side during the initial war with Asgard thousands of years ago, but now their time is running out. Algrim is called upon to make the ultimate sacrifice and is transformed into the monstrous Kurse. With a new and terrifying power, Kurse seeks to destroy Thor and Asgard in preparation for Malekith’s arrival.
Next: Burning of Malekith