The parasitic fungus known as cordyceps is grade-A, nightmare fuel. It infects a host body and replaces its tissue. In ants, for instance, the virus takes over the brain. The ant starts acting erratic, and the other ants will actually remove the infected member from the rest of the colony. As the cordyceps hijacks the hosts nervous system, the ant wanders around, finds some vine or something, and climbs up, at which point it latch on to the vine with its mandibles and its limbs and body become rigid, effectively attaching it to the vine.
Then, the cordyceps sprouts, as a fungal bloom bursts out of the ant’s head, spreading spore all over the area.
Fortunately, the cordyceps strains are species specific, and generally they only target insects. Humans are unaffected. At least in our world.
This doesn’t appear to be the case on the plane of Dominaria. That is a very humanoid looking creature there, which has been hijacked by a fungus. Cordyceps or not, the fungus we’re looking at here has taken over this victim’s body. This just looks like bad news to me. The fungus here is pernicious. Might be best just to stay out of the woods.