"This won't do," I realised after one hour of doing this that it wasn't going to work at all without dealing with the source of the problem itself, "I need to take down these portals first."
I noticed that my offensive attacks accumulated together, and kept pushing the outer force until they cleared an area of hundreds of metres.
But it wasn't enough to take down or even touch a single portal out there.
What I needed to do was obvious, and I didn't hesitate to do it. I controlled my chariot, moved towards the end of the protective zone cleared out by my offensive skills.
The moment I reached there, it seemed like the entire shields got moved out with me. This aided the offensive force at the forefront, pushing the outer force a bit further.
It was slow, but it was still a progress. I didn't stop summoning more shields, or activating the accumulated damage once per half a minute.