This monster would be more blobish than a lichen, it's form is not that stable. when it first appears, it is pretty large. then, it splits into two somewhat smaller versions of itself. then those split, and so and so forth. at a certain point, they cannot split anymore.
............and after they're done splitting, they take it one step further and just die.
But really it's a cool idea. I'd love to see this added.. possibly having it split every time it takes a certain amount of damage.