It technically remains a bubble from the outside but it will turn into a full scale illusion when they step in.
The illusions are simple- much more simple that what they faced in the last mission. It might be a freeze frame or a short scene showing an event, or a simple scene where people are talking to the person taking the trial, or it might be an object or even disembodied voices. They will step into it and be faced with what they fear- even though the scene is simple the feelings of fear are strong (as strong as they usually face fear).
To pass they need to bring the whole illusion down and they can only do that by accepting the fear as part of themselves and refusing to allow this to hurt them. If they try and run from the fear they can escape the bubble- and end up outside the cave without a crystal. If they freeze or can't complete the trial the fear gets more suffocating and the illusion sharper but eventually they will find themselves outside the cave.
Re: Questions?
The illusions are simple- much more simple that what they faced in the last mission. It might be a freeze frame or a short scene showing an event, or a simple scene where people are talking to the person taking the trial, or it might be an object or even disembodied voices. They will step into it and be faced with what they fear- even though the scene is simple the feelings of fear are strong (as strong as they usually face fear).
To pass they need to bring the whole illusion down and they can only do that by accepting the fear as part of themselves and refusing to allow this to hurt them. If they try and run from the fear they can escape the bubble- and end up outside the cave without a crystal. If they freeze or can't complete the trial the fear gets more suffocating and the illusion sharper but eventually they will find themselves outside the cave.