What are the tree monster statues on the Homestead?

[PixelDemise]

All the way on the right side of the homestead, a set of level 2 Tree Monster statues have been accumulating. Maybe I'm just a blockhead, but I can't seem to figure out what makes a new one appear. Is it supposed to be a counter for the number of year 10s beaten, or if you reach X number of that specific biome's Tree Monster killed?

I just got a 4th one, and nothing changed about them, so I'm guessing if there's anything they do, like a bonus stat, are there more to collect? There's enough space to the right of them to fit something else, so I'm not sure if I should keep checking on it as I finish runs or not.

[rapu ( ͡° ͜ʖ ͡°)]

I'm pretty sure they spawn after you beat the game with a new character for the first time.