Marlwolf

The Marlwolf (マオルヴォルフ) is a large digging mech piloted by Teisel Bonne. Teisel uses it to try and dig down to the Clozer Woods Sub-Gate since he could not get the key to access the ruins through the surface entrance. It attacks with large green energy orbs from its hands and Servbots throw bombs out the back hatch. The Marlwolf had invulnerable armor but if its hatch (located at the back of this robots head) is opened, it can be attacked from there. The Powered Buster's shot aimed onto its open hatch is very effective in destroying this boss.

Trivia
Marlwolf is a play of the word maulwurf, which means mole in German.