Producers are monsters in the bottom of the food chain. Their role is to take nutrients or mana and distribute it around the dungeon's soil. The only producers are slimemosses and spirits. As the bottom of the food chain they are also the most numerous and also the weakest of the bunch, and are eaten by stronger monsters.
Since these monsters are the start of the upward rise of nutrients and mana, if something were to happen to them the whole ecosystem would come crashing down. So the God of Destruction must take care of them or the secondary consumers will eat them all and be nothing but a pile of nutrients lodged in the walls of the dungeon. The fastest way for them to gather nutrients or mana is by forming a "H", "O", or "T" shaped tunnel to let them move back and forth inside.