Advanced Spell (D&D feat)
|Unofficial rules compendium
Advanced Spell (Metamagic)
Increase the number of hit dice the spell can affect.
Benefit: An advanced spell affects twice as many hit dice of enemies as a normal spell. Only spells who affect a limited number of hit dice can be cast as advanced spells. If the spell has a variable number of hit dice it affects, roll the dice twice. If the spell has a level-based bonus to the hit dice it affects, the bonus remains unchanged. An advanced spell uses up a spell slot two levels higher than normal.
Special: Advanced Spell can be applied several times to the same spell, with cumulative effects and costs. Applied twice, it requires a spell slot of +4 levels and affects three times the usual number of hit dice and so on.
Example: Tim the Enchanter is a ninth level wizard who considers how he can prepare an advanced hypnotic pattern spell. This is normally a first level spell that affects 2d4 hit dice of creatures, plus a number of hit dice equal to the caster level. Tim can prepare it as an advanced spell in a third level spell slot, and it will affect 4d4+9 hit dice of creatures, or use a fifth level spell slot to affect 6d4+9 hit dice of creatures.