Snow will be fighting off PSICOM troops with Shiva in Gestalt mode when play resumes. Autogestalt will kill all but the stronger enemy Orion and for this you may need Snow to join in with a few fisticuffs. If you’re struggling with this fight, select Retry and you will then be offered a chance to upgrade Snow’s pitiful Crystarium. It has been a while, after all. Focus on Sentinel and Commando first before making a start on Ravager. You should now find the battle much easier.
After your victory, you will be briefed on the Sentinel role of which Snow is a natural. The Sentinel acts like a tank because it absorbs damage, has a high HP value and can Provoke enemies into attacking the Sentinel instead of more flimsy characters like Hope. Go to the Paradigm menu after the tutorial and create Dualcasting (RAV and RAV) and Supersoldier (COM and SYN) to make dealing with PSICOM a little easier. Don’t forget to re-equip accessories for both characters too.
In the first battle against three Corps Tranquifex and a Bombardier, focus on the weaker enemies first and remove the Bombardier last. He has a large pool of HP and can take a while to kill so it makes sense to dispatch the weak enemies first. Head through the ice crystal wall into the next area after the battle.