The Hellspawn Tree is a tree on Earth that is pure evil, and can be used to summon huge demons by Mecha-Satan sometimes. The Hellspawn Tree is also the connection between the underworld and the fuel of all evil in the world. It was once chopped down by Deedle but was grown back by Agent 666.
The Hellspawn Tree is indestructible, and its roots grow underneath the ground all over the entire world. It is only able to break 3 days a century, when instead of using its powers to protect itself it charges it up because on teh third day a demon can do a ritual to make it into a sentient demon monster that is all powerful. But during those three days it is as easy to destroy as a normal tree, so a bunch of demons protect it. If after the three days are up and no one has done the ritual, then it goes back to being indestructible and the demons will have to wait another century to do the ritual. (Learn about the consequences of this on the Agent 666 page.)
The tree was originally created when some demons stole the seeds from the deedle stick 'o' power and modified to make them evil.