Alex tried to use the invisibility skill himself to hide just like that old man did, but due to his low cultivation base, he couldn't successfully employ it.
The light that cover him would break open at places randomly, allowing others to see him through invisibility.
'What do I do?' he thought. He needed a bit higher cultivation base to properly go invisible.
The old man was invisible, but it was impossible for his movements to do the same as well. No matter how good he was, his footsteps would leave a mark on the dune.
Alex looked at the sand around him to look for the old man. Just then, he saw a bunch of indentations on the sand. The old man was moving.
Alex waited for a bit and sensed the old man entering his spiritual sense range. He immediately slashed at the incoming old man and blocked his thrust attack.