...maybe not even a villain, but at least a strong antagonist; one who can offer new avenues to expand the lore and depth of the world introduced in the much beloved movie, Frozen. Many clamor for new characters, maybe a good villain, new settings and possibly, as some have suggested, a romantic interest for Elsa. With these things in mind, I may have found a character to tackle all of these challenges and fill multiple roles within the story while flipping through the annals of ancient mythology.
Janibas is a character from Teutonic Myth who was an obscure, but interesting, villain in a saga depicting the heroic exploits of the Knight, Dietrich of Bern. He is a powerful wizard, described as a dark rider cloaked in black, who casts spells from a mystical iron tablet (as seen above). In the story, he follows his father, the Giant King Orkise, into war against a sorceress named Queen Virginal, who had powers similar to Elsa's.
He certainly seems like a Gothic character, more suited to chase Hobbits in Middle-Earth than princesses in a Disney movie. Yet we've seen in the past that Disney has a deft hand at writing darker characters and stories despite its preference for fairy-tales (The Black Cauldron, Gargoyles and The Hunchback of Notre Dame as examples). The arrival of a darker character wouldn't mean an overall darker tone to something that should keep a light heart, but having extra-layers of interplay between characters from different genres (Fairy-Tale & Fantasy-Epic), time-periods (Renaissance & Dark Ages) and regions (Scandinavia & Germany) as well as roles within the story (protagonist & antagonist) would make for some interesting character dynamics and world building.
And he's got a cool name!
Obviously, for the purposes of a Disney movie, he wouldn't be portrayed exactly as the lore contends. The illustration above is my own take on how he'd be drawn in a "Disney-esque" style. If, as I'm thinking, he were to be portrayed as less of a villain and more of an anti-hero, he'd look less creepy and more sympathetic (and probably more attractive than the versions pictured beforehand).
If this character sounds interesting, I've implemented a theoretical premise for what Frozen 2 might look like if he were included...