Bibliothèque
To Berandor, Corporate dog, Nail, Mistwell, GruTheWanderer, roversaurus, KDLadage and Seule: Thanks!!
Yes, english is my second langages, and I do not know how I messed the 10/12 points font.
to die-kluge I say

, but you are right I forgot the how to enter problem, while as an afterthought it seems possible for a treant to enter, it depends on how you see the moving capabilities of a treant, so remove a rank in spot and listen, add one in use magic device and add in the treant's equipment a staff of size alteration.
To those who wants to use the treant, if you have song and silence, feuillu meet exactly the requirement for the royal explorer prestige classes (that's intentional).
And sorry for the lousy encounter, I made it so that it could be inserted in any adventure (like a dungeon crawl), I'll know better the next time.