Heya Mabel, your powers allow you to turn your body to Obsidian. Is it only volcanic glass, or have you managed other materials? And keeping to volcanic glass, have you tried stuff with/as "Pele's Hair"
I can control the density of my body from smoke to flesh to magically dense obsidian, but no other materials were granted by the blessing I'm afraid! I haven't tried the stringy-razor-thin strands, but that seems like a useful sort of shape to have in a given situation!
I'll have to try it out next time I have a chance!