Combat
Most of the combat rules will stay as presented in the Player's Handbook. However, here are some notes about styles and changes to things.
The general fighting style of this world has drifted strongly away from the heavily armored, mounted combatants. It is beginning to reflect advances in metallurgy and technological know-how, including the introduction of firearms. The swashbuckler is beginning to take the place of the knight in the hearts and minds of the people.
As such, most fighters are versed in several of the smaller weapons and many have begun to pick up firearm skills. Emphasis is now being placed on speed over power, and finesse over force.
Several schools teaching the finer arts of dueling have sprung up, notably in Luminaux. Felix and Jonathan's School of Swashbuckling and Derring-Do and Darkthorne Academy of Swordsmanship cater to rogues and fighters who wish to embrace the newer style. Even paladins have begun to shift away from heavily armored combat, and some have begun to study at a third dueling school, the Temple of the Guiding Light.