Shadow Stealth was a 5th Tier Spell, but it could exert the power of a 7th Tier Spell in Byron's hands, which wasn't much different from an Ultimate Spell.
Ultimate Spells weren't just stronger spells; the second characteristic of an Ultimate Spell was to display a spell's property to its pinnacle.
Shadow Stealth didn't have attacking or defensive effects, but it could allow a mage to hide, walk within the shadows, and avoid many detection spells.
Once this spell's characteristics were pushed to their limits, the user's body would be able to merge into the shadows.
By going through the shadows, mages' detection spells would be unable to discover the user. Magic traps and alarm arrays also didn't have too much of an effect.
