Ok here's the thing, if you are on the ground anywhere near this beast you are in for trouble. It's AC is its weakness, just about every attack is going to hit at the level you would be fighting one. If you are not at level 6-8 or above that beware, you are going to die.
They travel in large numbers and tend to be protective. The attacks they wield are horrific if you are caught full blast. Ambushing these or having a trap set up will be helpful. Anything to trip[ them while they are charging is good. Being off the ground / in flight is the best way to deal with this. Otherwise run for cover or set for charge (if you are bold enough). Be ready for a long fight with casualties.
Elephants make awesome war creaures too. If you're riding one they can take loads of damage and keep on fighting plus their like super intelligent.