Borg

Bolg is said to be the proof of a Magician. It is a defensive ability. It blocks out attacks with evil intentions. It also blocks out all physical attacks and magical attacks to some degree. It's strength, however, depends on the person. According to Maiyaz, if the Bolg is attacked by immense physical strength, then it can be crushed/destroyed.

Trivia

 * Ugo is the only person capable of crushing a Bolg with physical strength seen to date.
 * The Magic Ugo-kun is also able capable of destroying Bolg with physical strength.