This Dungeon Grew Mushrooms

Intro: “Oh! I know these gray mushrooms; they’re edible.” Facing adventurers who came to pick his mushrooms, Linden silently sprouted a pale blue mushroom among the gray ones. After a hearty meal, the adventurers all collapsed, poisoned and giggling on the ground. Luckily, another team rescued these unlucky fellows before they became monster chow.“Captain, what happened to them?”“Sigh, they dared to eat mushrooms here without offering sacrifices first. Outsiders are just clueless.”—Linden, who was summoned as a hero by someone unknown but reincarnated as a mushroom, found himself trapped deep in the dungeon, surrounded by monsters. To one day see the sun again, Linden used his hero cheat—decomposing corpses to plunder skills—to carve out a mushroom garden in the dungeon, planning to slowly counter-invade the surface…