Its drops will be encased in a small Obsidian Brick cube at where the head was, similar to the Wall of Flesh.
This boss can easily be rendered ineffectual by creating a thin land bridge between two large masses of Ash Blocks. Have it burrow through one mass to gain enough speed to reach your height, then simply dodge it and take your shots at the tail. Staying out on the bridge will leave you out of its reach, unless it burrows at a perfect angle to travel through the bridge. This is your best chance to do the most damage, just remember that it WILL catch up.
Remastered 22.214.171.124: Can now summon Magma Leeches minions