King of the Monsters is the sequel to 2014's Godzilla, which kicked off Legendary Entertainment's MonsterVerse, introduced the massive new version of the familiar giant lizard, and pitted him against two MUTOs (Massive Unidentified Terrestrial Organisms). Those two were a male and female of the same species, and were never officially given names besides "MUTO 1" and "MUTO 2."

The four known Titans in Godzilla: King of the Monsters are all pretty recognizable: Godzilla with his upright posture and distinctive back spines, Mothra with her luminescent wings, Rodan with his flame-edged wings, and King Ghidorah with his three heads. Though the latter three were dormant during the first movie, we also know where they're located: Mothra is in a hidden rainforest temple in China, Rodan is inside a volcano in Mexico, and Ghidorah is frozen in the Antarctic. However, in the second full-length trailer for King of the Monsters we see two Titans emerging that don't match any of those physical attributes or locations.

One is a creature with crab-like legs, tunnelling up from beneath an oil field, which looks like it may well be the spider kaiju Kumonga. The other is harder to see, but it is large enough that a mountain appears to have formed on top of it and it looks like it has a hard shell with spines. This Titan looks like it could be Anguirus, one of the very first kaiju featured in Toho's films, which made its debut in 1955's Godzilla Raids Again. However, a recent TV spot offered a better look at both of the mystery Titans, and the one emerging from the mountain could actually be something new entirely.

In addition to the two MUTOs, there were several other original kaiju designs created for Godzilla. One was a strange creature with many legs seen destroying a ship in the 2012 Comic-Con teaser, and concept artist Josh Nizzi also shared designs for two creatures that he worked on: a Pterodactyl-esque kaiju, and a six-legged lizard called Rokmutul (pictured above, on the right). Like Anguirus, Rokmutul appears to be largely based on the armored dinosaur Ankylosaurus. However, whereas Anguirus has a hard shell with many closely-grouped, upward-pointing spines (kind of like a cross between a tortoise and a hedgehog), Rokmutul's spines grow directly from its back and are slanted backwards.