An Ecologist Came to the Underground City

Hall travels through a fantasy world, only to find himself thrown into the 12th floor underground. Fortunately, a "Fantasy Monster Illustrated Book" helped him learn thousands of languages, collect monster information, repair the dungeon ecology, and establish friendly relations with all kinds of fantasy monsters. Improve the reputation of the group and absorb monster attributes and skills. Meet a monster you don't get along with? If the literary ones can't do it, then come to the military ones and destroy them! Unlock [Blackwood Treant] and learn [Wood Language]/[Bending Wood Technique]. Unlock [Scavengers] and learn [Pheromone Reception and Secretion]/[Paralyzing Mucus]. Unlock [Tree Spirit] and learn [Elf Language]/[Forest Charm]. Destroy the [Raging Wave Murloc] and learn [Aquatic Language]/[Slippery]. ... Adventurer's Guild: "Why did the monster on the twelfth floor come to the first floor?" Chamber of Commerce: "Purification crystal clusters? You can't exchange them with gold coins, you have to exchange them with land! What? You want to sell 1 ton?" Oath Knights: "Hall! As a human being, you colluded with monsters and indirectly killed many adventurers! Are you worthy of your status?" When Hall heard this, he revealed half of his face as a shape-shifter: "When did you have the illusion that I am a human being?"