Persisting Razor (3.5e Maneuver)

''It was only a quick slash across the arm, but the pain was incredible. The wizard struggled to keep his focus through his casting.''

Make a melee attack. In addition to normal damage you deal +15d6 damage, and any attempts at spellcasting at any point in the duration afterword must succeed on a Concentration check DC 10 + the damage done, as if they were damaged during the action of spellcasting. If they fail, they lose their spell as normal.

The damage is instantanous but the spell-disrupting effect lasts for 1 round/level or until the caster makes a successful concentration check to cast a spell. They may also make a DC 15 Heal check as a standard action to tend to their wound, which ends the duration. The spell-disrupting effect is pain based and does not function on creatures immune to to pain (generally constructs and undead).