I've noticed that enemies stop re-spawning after a while, and searchning oline suggest this will happen after an enemy has re-spawned 15 times. I'm currently not in a good spot to test this myself in-game though. I'm also interested if there is anyway to make enemies start re-spawning again after they've reached their re-spawn limit. It would seem there is some item which can cause enemies to re-spawn (and supposedly make them stronger), but I can't find out any details on what this item is called.
What I'm looking for then is confirmation on the re-spawn limit, the name of this item which can reset the re-spawn limit, which enemies the item will cause to re-spawn, and if there are any additional effects the item has outside of just re-spawning enemies.