20 level class that becomes Plant like??

[Khellendross]

I remember a few years back I saw a 3rd party source book, I want to say by Green Ronin, freeport about a 20 level class or maybe it was a prestige class that by the end you became plant like, it also had a deathknight and lich if I remember right. Does anyone know what book this is or of another class that is the same, besides druid.