A magical mist that is just wood
Behold the insides of the White Oak trunk. It looks like a magical, unicorn-related liquid. The most outstanding characteristic about this is that the bark looks like regular wood, but inspecting it deeper will lead to discovering the truth behind the multicolor mist.
While this definitely does not look like wood, it is; it’s fossilized wood. People from the Stone Age associated fossils with magic. However, fossilization is just a natural process that happens by the passage of time, with which scientists can study the remains of a living being after several years.