A spell that creates a Phase Inverse mana cluster, which can be used to block mana.
There's no particular technique involved—simply coating your surroundings with mana forms a barrier. Shield Magic is an basic yet practical defensive spell. Correspondingly, its fatal flaw is that when faced with high-density magic attacks, Shield Magic's barrier can be easily pierced, becoming a Maginot Line. Bulwark was invented to improve upon this flaw.