Ava
Ava, I'm not doubting your capabilities. I have the utmost faith in you and what you can do.
But these things are beyond demons, beyond gods, beyond comprehension. The Deep Ones themselves, when it comes to conventional weaponry, can only be hurt by extremely high powered weaponry and high explosives. And these guys are on the weaker end of the spectrum.
There's also the cult to think about. They're brazen enough to attack me in alleys, who knows how much power they actually have here. If they hurt you...
Spells that dry things out. I think if you can dry out a Deep One, it would die. Also powerful offensive ones, the more damaging and explosive the better.