Having a creature use gas balls is a pretty unique concept compared to all the charge light related submissions but it kinda ruins it a bit by incorporating said charge light into the flashbang attack.
I suggest dropping the charge light effect and add a suffocating effect to the "flashbang" attack similar to what happens when a player gets to close to a busting gas vein.
To keep the anti reaper/nameless nature of the attack, just make it bypass their armor like the basilisk spit can.
It's otherwise a pretty fitting and unique idea that doesn't suffer from ability bloat like many other suggestions.