Godstrike

Story Related. 

Mobus is the 4th boss you'll go up against and you'll start with a time of 5:30. After you defeat Drakhul for Awakened , you'll gain the abilities True Aim and Faster Than Light. You absolutely want to equip at minimum True Aim for this fight, though it's recommended you also equip your Beam and Overload for the active abilities. Go ahead and equip all 4 passive abilities since they don't cost anything. Mobus has 2 Phases:

Phase 1: Mobus will roam around with 5 individual sections on his back that you need to attack and destroy. As he moves around, he'll be shooting projectiles so just be aware of his location and try to dodge them as best you can. The Overload ability is really good on this section as well as your Beam as both can hit multiple sections at once. 

Phase 2: Mobus will still roam around but this time, the only vulnerable part he has is the end of his "tail". This is where your True Aim ability comes in super handy as it basically makes your attacks heat-seek the enemies, allowing you to direct your attacks straight to the tail. As he roams around, he'll still fire projectiles periodically but there will also be pods that appear in the play area. These will explode one at a time (you know which one is about to as it'll flash and beep). When they do, they'll either release projectiles, lasers or red orbs that, as before, will explode on impact. Do you best to dodge these while still going after Mobus. You won't really be able to rush this part since there's just a lot going on at once. 

Once you defeat Mobus, this trophy will unlock. If you need to visual reference of this fight, please see the video provided under Guardian . This fight takes place at 10:09.