They realized that when they attacked Lugh, the ones who died were all their companions.
Now that all the Fire Bats had flown away from Lugh's position, Lugh saw that all the Fire Bats had flown away, so there was no need for Lugh to kill them anymore. Lugh's task was to get the Sword of Light on the other side.
If these Fire Bats did not come to provoke Lugh, he would not have killed them.
Lugh could now go up to the iron chain. There were no more Fire Bats on the iron chain. Lugh used a few seconds to arrive at the Sword of Light.
The Sword of Light was a weapon of the Church of Light. Because it had a very strong killing ability against undead source beasts, it was very useful in a place like Skull Mountain where there were a large number of undead creatures.
The Sword of Light was surrounded by three angel statues.