You can activate the “Magmasaur heat” damaging effect by holding the secondary attack in until you have 100% searing spit, then primary attack (bite) and you will cancel the searing spit attack, and the charge will slowly go down, doing a good amount of heat and fire damage to any creature in a radius, this doesn’t trigger neutral creatures like trikes into attacking you, they can be killed as they don’t count the magmasaur heat damage as you attacking it.
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