Spell Conversion

Some classes (for example, clerics) can cast spells spontaneously. For example, clerics of non-evil alignment don't need to prepare healing spells: they can spend almost any prepared spell to cast a cure spell of the same level. Evil clerics have the ability to convert prepared spells into inflict spells of the same level. Likewise, a druid can spend a prepared spell in order to cast any summon nature's ally spell of the same level or lower.