Indeed—for
@StarChaser II, the
Thargoid war thread contains a concise overview of this! Below the weekly progress is each type of system, how it works and what to do. In this case, the sections regarding
Peripheries and
Matrix systems describe what you are seeing:
Peripheries
Each Maelstrom has Peripheral systems, defined as its outermost ten systems where Thargoids are present.
Each week, those Peripheral systems can receive up to 85% Peripheral progress, or 100% if a Matrix (containing a Spire site) is present.
The Peripheral progress is applied as a percentage, ignoring the system strength.
Matrix systems
Some systems contain a Thargoid Barnacle Matrix, revealed on the Galaxy map with the words
"Spire site present".
Destroying Orthrus Interceptors at a Spire site affects Peripheral progress (
old source).
Looting Spire Refinery Compounds affects Peripheral progress (
old source).
Spire Sabotage missions affect Peripheral progress, available at Rescue megaships.
It is indeed due to Spire site activity, it takes many dozens of Commanders to do it for whom I am extremely thankful, and it is being done exactly because it gives percentage progress with which we can actually clear a Maelstrom feasibly. Said progress stops at 85%, which it has just now reached this week, so nothing further is needed at Spire sites for the moment. That is until Thursday, when we will need another siege to complete the next set of ten systems!
As with most Thargoid war features, we get cryptic information at best. The only indication at all is the description below
Spire site present in the Galaxy map, which states
Expect Thargoids to prioritise defence of this location over peripheral systems. It was entirely upon Commanders to discover what
peripheral means and how a
prioritised defence works! It is worded from the point of view of Thargoids moving reinforcements to prevent any progress at the Spire, but obviously we are using that in reverse as a means to drain those other systems.
