Elena left the city after showing the guards the request form. They gave her a tag made using a stone and showing this tag would allow one to not pay a fee while entering the city again. Thanking the guards, she left the city.
The monster Elena was going to exterminate was Armoured Sand Scorpion. These were C rank monsters who were also the biggest threat to the people living in this city. A single Armoured Sand Scorpion was only as strong as a normal C rank monster. This city had several C rakers and they should be able to protect the city without much trouble.
But armoured scorpions liked to stay in large groups. And as a large group, they could very well be as strong as a weaker B rank monster, which was a great threat to the city. For that reason, adventurers living in the city regularly exterminated these monsters to make sure that their number did not increase too much.