Merlin was currently floating in mid-air. Wisps of Wind Element were wrapped around him, supporting him. This proved that the belt was indeed a Flying casting tool.
The belt must contain a mystical power which could cast a Wind-type spell. In that manner, it lifted the Spell Caster into the air, achieving the effect of a Fourth-level spell.
A Flying casting tool like this was very precious. It should be known that Flying spells could only be achieved by a Spell Caster who had reached the Fourth-level and constructed a Wind-type spell.
For Spell Casters below the Fourth-level or for Spell Casters who were Fourth-level or above but did not construct Wind-type spells, a Flying casting tool like this made things more convenient, and might even indirectly improve their battle prowess.