Abyss Monsters like these don't have much power.
An ordinary adventurer can handle one alone, an experienced adventurer can take out several, and an adventurer like Tamima Lu can kill dozens or even hundreds under the right conditions.
However, when the quantity reaches a certain level, it triggers a situation where quantity changes lead to qualitative change.
For example, now, with thousands or possibly more Abyss Monsters rushing at them, forming a black tide that relentlessly engulfs everything in its path.
If you fall in, you'll be torn apart in minutes, leaving no trace behind.
"Why did so many monsters suddenly appear!"
"How did they find us?"
People have no idea why they have been targeted by these swarming monsters. They neither unleashed any sound-and-light-effect-exploding Big Move nor ventured deep into the city, seemingly doing nothing to provoke this group of monsters.
Since things have come to this, they can only leave it to fate.
"Run!"
