The beast they killed was a Lightning-type beast. It wouldn't finish their quest, so they would have to keep hunting. But they still got their hands on a core that they could use to finish a mission later. They would just take a Lightning Magical Beast hunting mission and submit the Beast Core. That was generally what Marcus did for his Mercenary Quests.
Fantasy · WhiteNightingale
ch 0 1 Suicide
General · BAJJ
ch 0 7 Mr. initial task
General · BAJJ
ch 0 2 The Monster Transmutation System
Games · Qing Yan Yi Ye
ch 0 1 Divine Dominion
Games · Qing Yan Yi Ye
ch 388 Killing Boris, Ignoring The Lord of The City
Eastern · Panda Reunion
shipVIP
ch 0 1 Introduction
Interstellar Age
Sci-fi · Zentmeister