I do not fully understand the mechanism of the Ignis glitch, but I confirmed some backgrounds of the glitch.
- Ignis glyph shoots fireball sprites
- Shanoa goes into the boss room, an invisible sprite for the elevator will be generated at the regular position
- However, the elevator sprite will get zero-cleared (i.e. disappearing) only a few frames later
- Alternatively, dust sprites will allow Shanoa to use the elevator
In most cases (as far as I've tested), the elevator sprite will be located at 02113fe0-0211413f. The hitbox is at 021140b0-021140b7 (signed 16bit integers; x = 0x80, y = 0x80, width = 0x80, height = 0x20). Sometimes the sprite address might be at 02114140-0211429f or so.
In conclusion, Ignis can eliminate some sprites (in other rooms too). Putting other sprites (Globus for example) before shooting fireballs could change which sprites will be eliminated. I'm not sure if any other glyphs can do the same thing, and other good applications of the glitch.