A tip of the hat to Ravenloft's "Dread Companions" in the spirit of Studio Arthaus' rendition of the Land of Mists. While some GMs might argue that the Agate Companion is perhaps "too good for its price", players who think they can use it as a mere "cheap boost" to their animals will soon find themselves in a destructive relationship the likes of 80's novel Christine. Giving the GM full control of your animal companion under the premise of making your life difficult comes with a price. Your closest friend might soon become your undoing.
This creature has plenty of potental for interesting stories, the only reason why I don't give it 5 stars is because I see it more as a plot device than a monster as basically it wasn't meant to fight you as much as to pose a conundrum to be solved by indirect means.
Also, clearly this monster is adult material, not intended to be used by neither juvenile nor antagonistic GMs that would only use it for impregnating PCs left and right without a saving throw or playing Catch-22 with the party's paladin.
