: The civil war was still raging when the In Amber Clad jumped into the
: interior of High Charity. The station's defenses would have been running
: at max, and the Gravemind would have tried to keep them intact and
: running. There's a small question as to how they were powered after the
: Dreadnought left, but I would patch that plot hole by saying High
: Charity's power requirements had long since grown beyond what the Prophets
: could safely siphon off the Dreadnought's engine, and additional power
: stations were installed.

: So... the best energy shielding and starship weapons the Covenant can build
: directed by a hyperintelligent fungus older than the known universe,
: versus a fleet of lesser vehicles damaged by battle and divided by
: factional strife? My money is on High Charity.

In the High Charity mission of Halo 3, the Chief disables a set of 3 power generators just outside the Sanctum of the Hierarchs. Perhaps there were many such power stations in use without the Dreadnought.