Whatever the reason is, all the kaiju seem to have a red mist associated with them; Godzilla in particular gets a couple particularly nightmarish shots at the beginning and end of the first trailer, the first one showing him lighting up the mist with his charging atomic breath and the second showing the mist clearing to show his face, which takes a more classic approach with beady eyes on a twisted face.
The Anime
The ALAPU UPALA song. Multiple viewers have commented on how soothing yet deeply haunting and dread-inducing the "Folk Song version" is, especially with all the Soundtrack Dissonance in provides when heard within a story about physics-defying apocalyptic beasts arriving, as this song essentially heralds them. It first eerily plays in Episode 1 when the characters investigate an abandoned Old, Dark House, which is definitely the last place where you would like to hear something like that. Especially if soon after the lights flicker and you hear something roaring outside.
After a fairly cool fight between Jet Jaguar and Rodan, Rodan starts to fly away... only to die in midair and fall to the ground. At first it seems like he just perished from his injuries... then another dead Rodan washes up on shore. Then another one is found, then another, until eight in total are discovered. The final shot of episode 2? A swarm of Rodans erupting from the red tides, seemingly forming out of them, and filling the air.
In episode 4, the episode ends with a group of soldiers patrolling in case of a Rodan attack find an overturned van. The owners of the van are found nearby hiding in the nearby forest, but attempt to quite the soldier coming to help them as an unseen creature moves around the bush. Suddenly the pair runs to the road as the soldier turns, seeing Anguirus walk up to him and begin staring him down, cutting as we hear rifle shots quick get cut off.
Anguirus in general manages to be both cute and terrifying, with the scene of episode 6 of his revival strongly falling under the "terrifying" side.
Salunga takes all of the terrifying features of baboon and mandrill faces and gives creepy white eyes to them as well. This combined with many of its scenes, such as rising out of the red mist in a hunched-over position, creates a terrifying monster.
Episode 8 sees the return of Kumonga, revamped from a mere giant spider to an army of spider-crabs with drill arms. Kumonga's design has become much more sinister-looking, and the worst part is he now can regenerate. The injured crabs piece themselves together with slimy symbiotic tentacles resembling Hedorah—at one point Hedorah itself is visible, glaring at the protagonists before reconstructing Kumonga's body.
Episode 9 continues this and turns them into an army Jet Jaguar is barely holding off, mixed with a single individual with giant scythes instead of drills that can go toe to toe with Jet Jaguar. The rising tension of the scene alone makes them terrifying until Jet Jaguar is pinned against an army of them inside a burning building. To amp up their horror they're even the first monster to show their dead victims onscreen, them being dried husks wrapped up in their lair.
The closing shot of episode 9 is one in and of itself, as Yun and co. manage to get away from the spider-creatures by boat, and catch sight of the so-called Catastrophe starting to take place, as the red dust begins to form into a shape appearing like a more like a mushroom cloud, or as one commenter described it an "Interdimensional orbital strike".
The final few minutes of episode 10 sees Godzilla Ultima use its atomic breath for the first time. It's awesome, especially the charging up now coming with its own midair halo, but there's one particular shot - the fiery blue glow building in Godzilla's jaws from the viewpoint of what looks to be the tank crews on the ground. It's like the Death Star blocking out the sun just before it fires for the first time in Rogue One - the moment before a truly terrifying weapon is unleashed from the perspective of its first victims.
In episode 12, we find that not only did Salunga shrug off being iron maidened again...but he broke out quicker this time. We're treated to the sight of him slowly marching with dozens of crystalized spears impaling him from all angles, but not even seeming to notice or acknowledge they exist. Only one weapon has proven capable of halting him so far, and it's slowly losing its ability to do so.
The finale of episode 12. Just... holy shit. The entire scene just feels like the end times are coming closer and closer, with giant silkworm moths resembling Mothra fluttering around. And appearently, flying yellow moths symbolize oncoming warfare... And the song that plays in the background? It is called "Alapu Upala" and apparently according to some users, the song is about the coming of end times, brought upon by Shiva. And as we enter the gigantic red cloud with winds accelerating, we finally hear Godzilla roar. The finale is coming to a close, and Godzilla is the beginning.
All of the new incarnations of various Toho Kaiju are this. Rather than being ancient animals or the results of accidents/mutation, these Kaiju are extra dimensional entities that have intruded into our reality. Examinations of Rodan reveal a biology almost completely alien to anything humanity knows, Anguirus literally can see the future, and every last one of them is made of matter that simply defies all physics. And Godzilla? He’s so damn powerful, HE LITERALLY WARPS THE PAST, PRESENT, AND FUTURE BY MERELY EXISTING. It’s not hard to make a case that this could be the most horrifying incarnation of Godzilla yet. He's literaly a living cosmic disaster.
song. Multiple viewers have commented on how soothing yet deeply haunting and dread-inducing the "Folk Song version" is, especially with all the Soundtrack Dissonance in provides when heard within a story about physics-defying apocalyptic beasts arriving, as this song essentially heralds them. It first eerily plays in Episode 1 when the characters investigate an abandoned Old, Dark House, which is definitely the last place where you would like to hear something like that. Especially if soon after the lights flicker and you hear something roaring outside.