Practice some of the reality checks used for modern Lucid Dreaming checks. For example, one of the more common ones is to get into the habit of turning the light switch of and on or on and off (basically, flip the switch, and notice the change in lighting). In reality, if the source of light is altered (powered off) than the ambient light changes (Called the "No dip, Sherlock" rule). However, in dreams, this is not the case... if you turn off a light switch, the ambient light in a room does not change... even if you turn off all the lights. Our subconcious doesn't do that.
Another technique is that you should read a book backwards word by word... to get into the habit. Again, in real life, the letters correspond to words, but in dreams, the letters do not... but we are still able to process the expected information from the dream book, even though on inspection, the dream book has gibberish and if you're lucky, it will look like the alphabet too. Again, no real reason why, but I'm always struck that the brain in a dream state does not notice more subtle environmental changes related to a source of change.
Another option is that this order, in part of it's vowel, partially blinds or fully blinds their practitioners. Sighted people who lose their eyesight for some reason are often quite capable of lucid dreaming more than fully able bodied people. Again, this is some bizarreness, but blinded people will often dream in sight, which is an immediate tell that something is wrong as they can no longer "see" in the real world. Perhaps your illusion god achieves perfect illusions by manipulating the senses, which would be perfect to someone with all sense fucntions, but to someone with a disabled sense (deafness could work too), the sudden return of a sense that they did not have would be a clue that the world is not real.