How Long Is “Relentless Drag”?

In a desolate, lifeless world a tree grows parasitically from within a dormant war-machine. Unexplainably the machine awakens lost and confused, deciding to follow a flock of birds. As the machine ventures towards his unknown destination the birds make their home in his tree, rendering the robot into a traveling microcosm. The birds breed and other feral animals begin to follow, however the tree continues to rapidly grow, and the machine struggles under its weight. The robot's journey becomes increasingly dire, as the ominous tree makes his every step more difficult as time goes on, roots spreading to his joints, crushing his frame. He reaches his unknown destination, a coast of fertile soil, but the tree has become too enormous, the machine drags itself to the edge of a crater and pulls himself over, destroying what's left of him in the process, but the tree remains, safe at the bottom, a shelter and home for the robot's followers.