Although Basil had found the location of the two Goap's Generals along with their 100 legions, Iliana and him weren't actually near the Demons. They were 70 kilometers apart from the Demons.
The reason why Basil could see clearly that far was [Visualization]βhe still didn't have a high enough Magic Mastery level to allow him to see that far.
One might wonder why Basil didn't ask the Guide where the Demons were since the beginning, but Basil had actually done that. Since he didn't want to bother himself with manually looking for them, he had asked where they were to the Guide in advance.
He had been provided with an answer, but the answer had not been direct enough to give him the exact position of where the Demons were.
He had immediately activated [Visualization] afterwards, but unfortunately he still couldn't see the Demons he wanted to see with it. He figured out not long after that he could only target someone he had met.