Burning Knuckle (3.5e Invocation)

As a swift action, your unarmed strikes are wrapped in burning flame dealing 1d6 extra fire damage on your attacks for 1 round. You are considered armed, and do not provoke attacks of opportunity. On a critical hit, your attack explodes, granting you a free bull rush attempt. You do not follow your opponent which you knock back, and if you successfully move your opponent they fall prone.

The damage increases with your caster level, dealing 2d6 fire damage at CL 3, and an additional 1d6 damage every 2 levels beyond (maximum 10d6 at 19th).