Actually Illyana can potentially cast any spell concievable, with a very specific twist. She is most powerful while in Limbo, as such she can only produce spell, well powerful ones, while Limbo. In the past she has produced healing spells, complete replicas of the X-Mansion (in limbo) and complete alteration of Limbo as a whole. While on Earth she is very limited in her magic uses. Specifically her SoulSword, Magical Tracking with her scrying mirror & Teleporation spells (I know that her mutant power is teleporation, but she was effectivly able to teach Pixie how to produce a teleporation spell, which indicates that she could do it too.)
Blindfold's precog powers could def help her in the not seeing area, very similar to Destiny. She would basically see all actions beforehand allowing her to move accordingly. But Blindfold is also telepathic so she could use her powers so that she can she from the eyes of those around her. With these powers combined she can probably see better then most.
The term omega level has never fully been defined but here is pretty much the most common understanding of them. Omega mutants are the most powerful class of mutants. Omega mutants can control matter and energy without the aid of any tools or depence on an outside source. They have unlimited potential and are possibly even immortal. In addition to actual power, Omega mutants are not hindered by their powers. Meaning their physical appearance matches that of normal base-line humans, allowing them to live a normal life and blend with the normal population, if they wish.
While dazzler has almost all of these as a description even her newly shown possible immortality, she lacks in one major area. Dazzler while incredible in power and can fully manipulate light to any extent, she requires sound. The basis of her power is that she transduces sound into light. If she was able to bodily create light with no outside needs then she would most definately be an Omega Level Mutant. This is not the case, she requires sound to make light. NO sound, NO power.
This would define Dazzler as an Alpha-Level Mutant.
ok so this is probably super old to be responding to, but I'll still reply since the answer was never fully explained.
Banshee is the correct answer. I can't quite recall why he was back at the mansion specifically but he was just returning and settling in. He stepped out of the Men's Locker-room he decided to walk through the mansion and he was noticing "werid" happenings with his fellow X-Men. i.e walking behind and hiding from Psylocke (psychic ninja?? Psychic?? how was he detected by her.) A couple of other odds things occurred and he wanted to talk to some of the other X-Men about it but every time he found a different team-mate, they would act weird and he decided against the interaction with them. Until he met up with Bishop and Iceman (i believe) he went up to Bishop and began a conversation with him. Ultimatly he was testing "Bishop" and mentioned something something to the effect of Professor X no longer being paralyzed or that he could walk. Without a reaction what-so-ever "Bishop" acknowledged him and didn't attempted to correct Banshee. Reason being: it wasn't the real Bishop but actually The Phalanx in the form of Bishop.
At this point he decides to run a check on the mansion to see who was on the ground and the system pointed out that only for individuals were in the or location on the grounds. Those being White Queen (Emma), Jubilee, Sabretooth and Banshee himself.
This the begining of the "Phalanx Convenant X-Men" and their search for the future members of Generation X.
*its been a long time since I've read the comic soooo I don't remember all the specific details. but this is pretty much the just.