These guys are actually quite good climbers, I have a mining outpost on top Eldritch Isle on Crystal Isles and can easily keep two industrial forges filled and going at all times. Just watch out because they take quite high fall damage.
Magmasaur is able to destroy ALL STRUCTURES utilizing its searing spit. While it is a walking forge it produces metal at the same rate as a refining forge. You can use the jump button to taunt other creatures and when holding searing spit use crouch to erupt. (This attack pushes creatures back and leaves magma everywhere) it is breedable in lava. Hope this helped