The season finale of The Mandalorian dropped a reference to one of Dungeons & Dragons' most famous monsters. In the season finale of The Mandalorian, former Rebel trooper Cara Dune (played by Gina Carano) mentions that the Empire uses Mind Flayers during interrogation. While it seems to be a reference to some kind of robot or device, fans also noted that the Mind Flayer shared a name with the "big bad" of Stranger Things....and one of Dungeons & Dragons' most popular monsters.
The Mind Flayers (or Illithid) are a race of psychic and intelligent creatures best known for their hive mind and for their desire to feed on people's brains. Their powerful psychic abilities and plans for world domination make them a popular monster in D&D campaigns and led to Mike and his friends naming their mysterious foe after the creature in Season 2 of Stranger Things. Notably, the Mind Flayers seem to be main threat of the upcoming video game Baldur's Gate III, as the first trailer showed an unlucky soldier being forcibly transformed into a mind flayer.
While we don't know exactly what the Mind Flayers are in Star Wars canon, we have seen one creature with similar abilities already. Rogue One introduced Bor Gullet, a member of the Marian race that can psychically read thoughts. Like Mind Flayers, the Marians have purple skin and tentacles on their face and can forcibly extract information from their victims' heads using psychic powers. According to various Star Wars sources, Marians were most often used by the Empire, so it stands to reason that they are the Mind Flayers that Cara Dune was referring to.
The Mandalorian isn't one to waste Star Wars canon, so there's a pretty good chance that we'll eventually see a mind flayer appear on the show. Unfortunately, we'll have to wait until 2020 to get more Mandalorian goodness, as the first season has already ended.