Its not the items it eats, its the weave itself, the magic itself.
So,... well, the excuse could be if it eats away the magic that is used to change the tadpoles, the tadpoles would assume their normal functions or do it suddenly all at once, so that would not be a good thing to do. Still... one wonders how exactly that magic devouring orb doesnt devour any magic that comes close to it, including the one around or inside the tadpole.
Nightsong couldn't do shit about tadpole either. And both are somewhat connected to Shar, Nightsong serves her and Gale's problem being shadow weave. Maybe it's about nature of magic shielding the tadpole. I am pretty greenish about the DnD lore but could it be that this "shield" magic is coming from Shar?
