The main ones are:
A player can now have up to 3 Reinforcement Gladiators in their Gladiator stack, and no limits as to how many of those three can be brought into play. Also, Reinforcement Gladiator's Maintain costs (if any) are no longer mandatory. There are no mandatory Maintain costs.
Cheer is generated whenever a Gladiator attacks a character, not just an Unset character.
A Protecting or Intercepting character can deal Defense Damage.