Silent Killing in the Darkness

"REAP SPIRIT, ETERNAL DARKNESS," after Soulayer entered [Enraged] mode as Stark tried to hit the jar between its neck, it suddenly activated two skills.

…

[Skill: Reap Spirit]

[Description:] Soulayer can harvest the souls of fallen foes to strengthen itself during battle, however there is a limit to that, and the backlash it receives can be very high if it uses too much power

…

[Skill: Eternal Darkness]

[Description:] Plunges the world into darkness, giving it an incredible advantage as it is used to fight in the dark because of the [Soul Graveyard] rift.

…

'Soul Graveyard…?' was what confused Stark the most, doesn't that mean this monster was in another much more powerful rift, yet came to this one and became a boss.

In the end, he didn't have the time to think too much about it since…

"REAP SPIRIT," Soulayer kneeled down, then put both of its arms inside of the black water.

~FWISH, FWISH~