You caught a glimpse of fire-demon Surtur in that bonkers new Thor: Ragnarok trailer. He's the giant face Hulk leaps towards all the way at the end, and there's also a very large body attached to him just off screen, a body that director Taika Waitit did some of the mo-cap for. As with most faces, Marvel's own Galadriel-controlled Balrog will also have a voice, and a very cool voice at that.
Surtur will be played by Clancy Brown, who you may know as the prison guard from famous tax-evasion rom com The Shawshank Redemption. He also plays General Eiling on The Flash, a guy who had a psychic gorilla speaking through him the time he showed up, and his stellar voice work also includes villains like Lex Luthor on Superman: The Animated Series, Dr. Neo Cortex in the Crash Bandicoot games, and the role he was born to play, Red Hulk/Thunderbolt Ross in Hulk and the Agents of S.M.A.S.H.
Since I only remember him from serious properties like superhero cartoons, Spongebob Squarepants, racing games and the IMDb Top 250, the powers that be have asked to remind you he also played Mr. Highlander in The Kurgan, Starship Trooper #7 in Sgt. Zim's Space Vacation, and Pet S. Emetery II in Sheriff Gilbert: Dog Murderer.