A Dragon dying and splitting up its essence into 9 parts, giving birth to 9 'offsprings'- each a Kaiju different in appearance from the normal Dragon. These offsprings each have their own territories but they could fight with each other since devouring their siblings is one way to make themselves stronger.
This Dragon is part of the Original Creation and its death means that the Basic Elements that are part of the Dragon will separate without the Dragon as the "central glue" to hold them together.
These Basic Elements might seek out compatible lifeforms to bond with OR be accidentally/coincidentally 'swallowed' by existing lifeforms with the result that some sort of 'mutation' occurs, giving rise to Kaiju 'offsprings' of the Dragon.
submission 1- a mountainous continent that is shaped by the fight b/w two of these Kaijus whose territories border each other: their footsteps create valleys, they kill each other and their spines become the two tallest mountain ranges, their decaying bodies enrich the soil etc.
Submission 2- a Kaiju that has its domain in a submerged continent, a cross b/w a water serpent and a swordfish (or maybe a unicorn is more appropriate, basically, it has a horn sticking out of its forehead). Its milk feeds its children but also the intelligent races living there.