If the Ymir survives long enough to be destroyed by the Axon’s main beam weapon, then you win.

Don’t botch the diplomacy job you did in Scene 12 by prematurely attacking rebel aliens.

Focus on protecting the Ymir.  Everything else is secondary.

Give the Ymir a wide berth.  Its hull fields are invisible and will kill you dead, dead, dead.

When attacking aliens strafing from behind the Ymir, be careful your stray shots don’t kill the ship you’re protecting.  Come in from angles to minimize this risk.

Don’t get lured too far BEHIND the Ymir.  Since it’s moving quickly, you’ll have a hard time catching up.  Conversely, don’t be afraid of going quite a way in FRONT of the Ymir.