The elders and disciples could not see what was happening on these islands because something like this was impossible even for the strongest elders of the biggest sects to do, which was good for Zhang Yi who could use all his skills without bothering to reveal his secrets.
But Zhang Yi thought he would only be in danger if he was surrounded by hundreds of enemies and he would just have to use his qi clone technique to be able to beat all 1,000 enemies easily, so it was impossible that he needed to use all his techniques to win.
The first 10,000 disciples entered 10 different islands and after a long time only 10 disciples would leave these islands, Zhang Yi found this an interesting idea, because almost all of the disciples were between the seventh level and the ninth level of the soul refinement realm.