The virus that mutated the plants on earth had evolved and manifested a sinister appearance for itself. The Heart of Tree was a creature that dwells under the "World Tree" and controls every mutated plants within it's territory. Human bodies were attached on it because the plants would only target humans for nutrition and it is implied that it had consumed countless human during it's reign. It's body was made up of vines extended from the root of the tree which would protect it's "heart" and also serves as it's offense weapon.
This creature had challenged me to design a complicated monster that does not base on any animals that could be found on earth, my only research source could only be the sinister monsters that is heavily designed to have their own story. However, it was really fun while working on this as it was my first time and would definitely try to push myself more to paint better monsters.