A Phaser is one of the special abilities an elf may manifest as. Phasers have the ability to break down their cells (similar to light leaping) in order to walk through solid objects and other things, such as walls and swords. Some talented Phasers are able to disassemble some parts of themselves like Blur, who appears partly visible and smudged as part of his disguise.
Blur has demonstrated the ability to sense an object's inner functions by passing an intangible hand through the object. To what level Phasers can sense through this ability is unknown.
“You just walked through a wall."..."Phasers do that sometimes.”