Advanced Materials are Goblins

Transmigrating to another world, while other adventurers followed the ancient strategy of "warrior tanks, mage deals damage, priest heals," Renn discovered that he could obtain the core talent of every monster he killed, leading to a complete absurdity: the berserker's [Blood Frenzy], honed over ten years, was obtained by slaying a single goblin. The mage's prized [Fireball] was merely a generous donation from a mutated shaman. After slaying the Goblin King, he accidentally acquired the [King's Aura]. By swiping goblins, Renn successfully transformed himself into a well-rounded warrior. Until one day, the Demon King's army besieged the fortress, and the heroes trembled in fear. Amidst the despairing gazes of the crowd, Renn silently pulled out a manual that lit up all the monster icons. "Don't panic." "I'll go to their lair behind the camp and get some magic immunity..."