Costly Defense

Costly Defense compresses a known elemental spell inside the caster's body until the first blow breaks it loose. Fire burns across the skin, acid rises as caustic vapor, or lightning crackles around the caster, making the danger visible to anyone who approaches.

When casting Costly Defense, choose Acid Splash, Fireball, or Lightning Bolt. The caster must know the chosen spell at the same level as Costly Defense. Only the Costly Defense slot is spent. A Red Dragon may use its Fire Breath in place of knowing Fireball, but still uses Fireball's listed damage for the explosion.

The first attack that deals damage to the caster resolves normally, then triggers the spell. The caster and every creature within 5 ft take 125% of the chosen spell's listed damage at that level and caster level. Creatures farther than 5 ft but within 30 ft take half that damage. The explosion allows no Save.

Costly Defense borrows only the chosen spell's damage dice and element. It does not copy its globules, projectiles, areas, overlapping damage or secondary effects. Use the listed damage per caster level once, including at level 10, then increase the result by 25%.

The caster receives no protection from Costly Defense against the explosion. Armor, resistance, immunity and other protections against the chosen element apply normally.

The spell ends after this single explosion. If nothing triggers it, it lasts for 1 round per caster level. The caster may dismiss it early with another Swift action.