Pillar of Fire

The pillar of fire is the strongest spell a Master of Fire can summon, as stated by Amos in the Red Pyramid. Zia summons it in order to deter Desjardins, thus allowing Carter and Sadie more time. It is shown to be a massive pillar that burns through anything. It will not be destroyed until the caster loses the energy needed to sustain the spell. The time it remains varies depending on the magician's strength and ability. It is important to note that while powerful, the spell leaves the caster defensless to other magical attacks and without magic power.

The Red Pyramid
Zia casts the pillar of fire when she reunites with Carter at the "place of the crosses". It relentlessly pursues Desjardins, rendering him useless as he tries to avoid it. Desjardins tries casting a spell to destroy the pillar, but all he can do is manage to keep it at bay.