This is Ygg my testing world building project. It is totally free to use and anyone can make stories, characters, concept art, etc. as long as it's in the context of the world and story.

Collusi are massive monsters made up of the multiple parts of living things such as animals, plants, and fungi. They are usually solitary but there are a few that would tolerate the presence of Fiends. Collusi are the physical manifestations of chaos within living things. They can lay eggs or give birth to Fiends or Young Collusi.

There are four stages of Collusi:

1. Young Collusi were recently Fiends who became Collusi through cannibalism. They can reach from 10 to 15 meters tall. Once they become Collusi they no longer need to cannibalize to get stronger.
2. Mature Collusi are Collusi powerful enough to reproduce a small pack of Fiends [4-6]. They can reach from 20 to 25 meters tall.
3. Elder Collusi are Collusi powerful enough to reproduce a small horde of Fiends [12-20]. They can reach from 40 to 50 meters tall.
4. Ancient Collusi are Collusi powerful enough to reproduce a horde of Fiends [40-50] or a pair of Young Collusi. They can reach from 80 to 100 meters tall.

Fiends are the offspring of Collusi and just like their parents they are made of multiple body parts but are separated into three categories. Beast Fiends, Plant Fiends, and Fungal Fiends.

1. Beast Fiends are Fiends that appear as multiple animals put together. They are the most active and generally travel in packs or hordes. Some of these groups seem to develop a pecking order with their rank and leadership determined by age and strength. These Fiends constantly invade the territories of mortals thus war between them is seemingly constant. These Fiends can only use life magic of related to beasts.
2. Plant Fiends are Fiends that appear as multiple plants put together. Unlike their Beast counterpart most Plant Fiends are solitary and are primarily ambush predators with various types of them specializing to hide in thick vegetation, underneath sand and mud, and within crevices of rock, etc. Not only that, most Plant Fiends are territorial and do not tolerate other Fiends except for Fungal Fiends. If another Fiend, besides Fungal Fiends, invades their territory the Plant Fiend will actively hunt them down if they are not outnumbered or overpowered These Fiends can only use life magic related to plants.
3. Fungal Fiends are Fiends that appear as multiple fungi put together. Their hunting strategy is very similar to Plant Fiends except they prefer dark and damp environments such as caves or the deep parts of forests. Unlike Plant Fiends are migratory and prefer to eat things that are already dead as they are more scavenger than hunter. This may be the reason why Plant Fiends tolerate them as they prefer to digest the soft fleshy parts of their victims whilst leaving the harder and tougher parts for their Fungal brethren to eat in order to keep their territory clean. These Fiends can only use life magic related to Fungus.

Fiends can become Collusi by cannibalizing other Fiends and Collusi. By doing this they absorb the bodies and powers of their brethren. The largest Fiends can reach up to five meters tall or long. Once they've reached ten meters they are considered Young Collusi.