```
If he were to exhaust his magic power now, then the timeframe for this breakthrough would have to be postponed, following the time needed for the recovery of his magic power.
This is giving up the future for the present, and it's a foreseeable future at that.
In summary,
Although Lu Yuan could use the Marsh Technique, the cost of using this spell is quite significant in a sense.
Or to put it more harshly,
Given the choice, he would probably prefer sacrificing tens of thousands of people instead of using this spell, saving that magic power for later.
After all, the deaths of tens of thousands can be made up for by Chu State after a year or two.
But without so much spiritual energy, Lu Yuan has no way to restore it.
Compared to renewable manpower, the presently nonrenewable spiritual energy is somehow more precious.
Reality is cruel but very much real.
