The final battle of Avengers: Endgame almost included the Dark Elves from Thor: The Dark World as part of Thanos' massive army. As the culmination of a 22-film story, Avengers: Endgame ended the only way possible, with nearly every character imaginable sharing the screen. Heroes new and old joined forces at the remains of Avengers HQ to face Thanos once again, but this time as a united group and with a lot more reinforcements. The heroes were joined by Ravagers, Asgardians, and so much more, and all of them were needed as Thanos' forces were even bigger here than in Avengers: Infinity War.
When he made his attack on Avengers HQ and was ready to completely wipe out humanity, Thanos stood with the Outriders, the Chitauri, and Sakaarans behind him. They were also joined by Thanos' children Ebony Maw, Cull Obsidian, Proxima Midnight, and Corvus Glaive. As massive as the army was, it turns out that earlier versions of Avengers: Endgame could've seen the Dark Elves fight in support of Thanos too.
Slash Film recently interviewed Matt Aitken, the visual effects supervisor for Weta Digital - who worked on the CGI for Avengers: Endgame's final fight - and received this piece of information during the conversation. Aitken was asked to detail every different faction of Thanos' army, and said, "At one point, there were going to be - potentially dark elves were going to show up, they didn’t make an appearance." While they may have been considered, Aitken went on to clarify that this idea was discarded before his team ever did any work to include them.
The dark elves were mentioned, but we never got as far as rigging them or making them for the battle.
If Aitken and the team at Weta never had to create the Dark Elves soldiers for the final fight, this idea never made it too far in the development of Avengers: Endgame. Thanos' army was big enough as is, and since the MCU hasn't reused the Dark Elves since 2013, there were more than enough alternative members to include. That said, it would've also just strengthened the ties Avengers: Endgame has to Thor: The Dark World.
While the Dark Elves appear to have only been considered to make a return, the potential of them being part of Thanos' army is a fascinating possibility to explore. This could indicate that after Thor defeated Malekith in Thor: The Dark World that Thanos managed to recruit the remaining members of the race to be part of his army, further showing just how much power and influence the Mad Titan had in the galaxy. It would also have raised the question of why haven't we seen them since this moment though, as they should've then been part of Thanos' forces before. Whether the Dark Elves ultimately aligned themselves with Thanos or not in the MCU, they would now be free from his commands after the events of Avengers: Endgame either way, paving the way for them to possibly return down the line.
Source: Slash Film
