A Good Tool
Nikolai breathed out as he finished absorbing the crystals. All of them rewarded him with three stats points. Furthermore, as he waited, his undead went ahead and started hunting more monsters.
The monster can be E-rank, but it could not defeat his undead monsters. These monsters were organized and attacked as one, unkillable, and used the darkness.
However, very few monsters can survive the darkness. Most of the monsters they encountered were dark beings, but they awarded Nikolai more mana crystals than normal monsters did.
The dark beings were not undead, and they were not immortal. Humans thought of them as immortal because usual elements were weak against the dark element. Unless someone has the element of light, or holy powers, or a lot stronger than the being, then they cannot kill a normal dark being.