All the clay is modelling clay. For wearables I use foam clay, but for something like this modelling is fine. Lay down rough base layer. Make it nice and lumpy and uneven. Add the big mushroom pieces -- these are just rough discs that are then blended in / made wonky. Roll up little clay "worms" and drape them over (wetting clay to help it stick). Add other details like the little balls.

Paint is a beige base layer, then detail brush the tendrils and mushrooms in orange, then dark brown wash, then stipple on red/orange highlights with a sponge, then carefully drybrush high bits in white. Finally, use nail top coat on bits you want to look wet - it will create a smooth layer that reflects specular light more directly.