Fungus
Fungi are not plants. They do not photosynthesize. They secrete enzymes, break other bodies into soluble parts, and absorb what they need. Much of a fungus is underground or inside wood: hyphae, thin threads that branch and fuse.
A mushroom is a fruiting body. The work is the Mycelium. Rot, Yeast, mycorrhiza, Mold, and Spore on the map feed Fungus.