Source: Epic Level Handbook
Your spells manifest with a distinct theme or appearance.
Prerequisite: Arcane spellcaster level 1st.
Benefit: Due to the unusual appearance of your spells, the DC of any Spellcraft check made to identify a spell you have cast increases by +4. In addition, you may designate one spell you know per spell level as a thematic spell and cast it at +1 caster level. As you gain access to new spell levels, you can designate new thematic spells; you don't need to select this feat again to acquire new thematic spells. Nearly any theme is possible; so long as you can describe a visual link for unification. For example, your theme might be "lightning," "spheres," or "screaming skulls." If you choose spheres as your theme, your magic missiles might take the form of glowing spheres of light, and your summoned monsters might emerge from mysterious rainbow-colored globes. If your theme is "lightning," your haste spell might manifest as a bright green spark that leaps from ally to ally. You can't use this feat to make your spell manifestations invisible, nor do your spell thematics change the type of damage a spell deals, regardless of its appearance. This feat supersedes the version found in Magic of Faerûn.