Once You Get The "Chief Technician" And "Letterman" Achievements, You Are Able To Make Siege Breakers.
Once Crafted, Use This Barricade To Push Your Way To The Portals.
- Your Spare Archers Follow Along.
- You Can Even Drag It Backwards To Prevent Big Enemies From Thwacking It As Much While Your Archers Unload
- Your Mechanic Will Fix It After It Takes Damage, But It Can Not Be Under Attack While She Does This.
Get Close Enough To Let Your Archers Tear That Second Portal Down And The Achievement Is Yours. Be Careful, This Portal Spawns Some Mega Slugs To Try To Stop Your Advance The First Time You Attack It.
Good Luck!