Found it!
Hang Yu discovered the anomaly in the Magma Lake.
In the Magma Lake, there were some scattered black reefs, and some reddish-brown objects.
If you observe closely, you'll find that the reddish-brown objects move slowly; they aren't reefs, but a gigantic monster, fully immersed in the magma.
"Bai, start controlling the field."
"Er Gou, assist in blocking any stragglers."
His two subordinates immediately followed orders. Bai activated the skill Illusion Dust to cover the surrounding area, preventing the nearby monsters in the canyon from noticing once the battle starts. Er Gou, on the other hand, stationed his clone at the canyon's entrance, ready to pounce on any wandering monsters that might come their way.
Hang Yu had already used the Weapon Contract in advance.
He took out a level 15 light blue longbow.
This longbow was the strongest war bow found when looting Sand Spring City.
