Tactics: what do you think? Entangles, slams, casts unpredictably?
How about CR 22?
I would not kick up a fuss about that.
Let's go with that and see if Shade objects.
Of course he likes it.
Tactics: The Tree of Wailing Souls first entangles its victims, sometimes waiting until they encamp on the surrounding hill. Then it comes to life in a whirlwind of slams and sometimes spells, which it casts nearly randomly. When it absorbs a soul, it manifests that head in order to intimidate its remaining opponents.
Sure, that's fine.
Just description, flavor, and language, I think.
I vote that it can speak any language known by one of the absorbed souls, which is essentially anything.