The normal stinger is simply a stabbing weapon that doesn't inflict any other interesting afflictions.

The unstable stinger is, you could say, just an upgraded version of the normal stinger which also has a tiny chance to inflict the husk infection.

You can get unstable husk eggs by killing mutant monsters, and you can use them on husked monsters to mutate them.

Sounds like a chicken-egg sitation here...l you need egg to make mutants and can only get eggs from mutant. Hmmm so far havent seen a single mutant spawn naturaly