Leon didn't have time to create steel spears, he could have created them earlier, but since the moment he discovered his hometown had been nuked, his mind stopped working like usual. That being said, Leon had to be careful. He didn't have potions or herbs with him so that he could run out of mana.
First, Leon decided to focus on the eye-ball monsters, their thunder attacks were powerful, but since their entire body was a weak spot, he knew he could kill them fast. After confirming that they could easily die after being hit by a single Water Bullet, Leon spammed that without remorse.
Eventually, the monsters noticed that something was attacking them from above. Soon, they saw Leon above them. Despite being able to fly, the eye-ball monsters were quite slow. Leon finished them before they could approach and attack him.
"I see... so their attacks have a certain range of effectivity."