JahSepp
The jahSepp were a species of sentient multidimensional fungus native to the mycelial network.

Biology
The natural form of the jahSepp within the mycelial network was as swarms of green sparks. They broke down all matter entering the mycelial network to make it useful in new ways, so as to progress the life cycle. The  of the yeel tree was a deadly toxin to them. ()

The jahSepp appeared unfamiliar with the concept of tears. ()

History
They claimed to have been living harmoniously until their ecosystem began to be irreparably damaged by what they believed was Starfleet's utilization of the spore drive. Believing their entire species might die,  broke through the confines of the mycelial network at great personal risk, and managed to reach Sylvia Tilly. In her, it found the memory of May Ahearn, and started using it to manipulate her. During a mission into the network itself, the Discovery crew discovered that the jahSepp's "monster" was actually Hugh Culber who had been murdered months before and was inadvertently killing the jahSepp while defending himself from the network's attempts to get rid of him as a foreign body. At the crew's request, the jahSepp resurrected Culber for them. ()

After arriving in the late 32nd century, Commander Paul Stamets advised the Federation team working to duplicate the spore drive on how to avoid harming the jahSepp. ()

Fungi
Species