Not D&D Saturday Gaming
A demon. Anything you can find in a D&D monster manual is an Oni. Oni tend to be very powerful. Just being near an Oni will give you the Shadowlands Taint. Being struck by an Oni several times is really bad mojo for your character, even if you live through it. Chances are I won’t do much with the Shadowlands Taint. It’s a lot of bookkeeping and not a whole lot of fun unless it is relevant to the plot.