In the end, the old mage fainted from mana exhaustion.
He was weaker than me in the first place, so he ran out of mana faster.
It was to be expected since I did not think some of the people stronger than me had larger reserves than me.
After the old mage fainted, since I didn't want to kill him, which turned into a battle of attrition while he got beaten, I trapped him by using my origin ability to create earth chains and tie him to the ground.
After doing so, I went to help the emperor's soldiers and started attacking the ogres to minimize the emperor's losses.
In fact, it wasn't until I started to concern myself with the emperor's soldiers that I found out that there weren't that many losses.
Some died, and many were injured, but even among them, out of the one thousand five hundred soldiers that came with the emperor, I'd say that only about 200 were dead.
When I observed more, I discovered why.