I'm Just Using Monsters to Make a Gu

There is a small space in Elian's body, where the souls of monsters are imprisoned, and his greatest pleasure is to watch those souls fight each other. The winner will swallow the other's soul fragments and evolve—— [Orc] defeated [Goblin] and gained a new ability [Cross-species Reproduction]; [Orc +1] defeated [Skeleton] and gained the new ability [Hard Bones]; [Orc +2] defeated [Slime] and gained a new ability [spitting mucus]... Eren looked at the new abilities he had acquired, and then silently turned his head to the wild boar not far away. There will definitely be a powerful ability this time, right?