It seems more straightforward having everything in the Special Quality.
I'd put the "time to grow" bit after the "destroying it does no harm" bit.
How's this:
Extraplanar Lure (Su): An ihagnim's interior has a transdimensional conduct to a lure on the Prime Material Plane. This lure is the magic item known as a bag of devouring, and any creature destroyed by the bag counts as being devoured by the ihagnim (see above). Destroying a bag of devouring does no harm to the ihagnim connected to it. An ihagnim can have only one lure in existence at any given time. If the bag is destroyed, it takes an ihagnim 1d4 weeks to grow a new lure. It takes an ihagnim an hour to either create or absorb the lure's transdimensional conduct, to either "cast" the lure onto the Prime Material Plane or "reel in" the lure from another plane. Reeling in the lure causes the ihagnim's bag of devouring to appear on the Astral Plane in a space within the monster's reach.
If a ihagnim's bag of devouring is transported to the Astral Plane, the ihagnim infallibly senses its position as if using the discern location spell, and can travel to the location of its bag in 1d12 hours.
I added a bit about how the ihagnim sends its lure to the Prime Material and then elaborated it further by having it be able to retrieve the lure. I was thinking that the ihagnim is essentially like a fisherman randomly throwing a baited hook (the
bag of devouring) into a lake (the Prime Material Plane).
If it's just tossing the
bag to a random spot on the Prime Material, there's a good chance there's nothing to catch in the area, so it'd be very useful to the ihagnim if it could reposition its lure and try its luck at another "fishing spot."
