Sprul-pa from the Runequest Quickstart Scenario "The Broken Tower".
I ran the adventure for a group of friends and, since there was no handout picture to show to my players, I tried to draw them based on their description: These spirits swim through earth, but manifest their bodies of vines, blood and soil manifest only through the skull of a cattle.
Since the ancient Theyalan ruin was littered of cattle skulls, sacrifices to the local earth goddess, there were a-plenty!