Info about marronians in general as well as a depiction of a standard inland Marronian can be found https://www.furaffinity.net/view/60838026/

The volcanic Marronian is a variant of marronian that live much farther inland than most, where the concentration of smoke and volcanic activity is much higher, they often have a lot more horns, or horns that branch out like antlers, and spikes, their tail is extra painful to relieve a sting from, as a volcanic marronians tail actually produces a spike that sticks into the flesh after delivering the initial sting.