My version of combat reactions isn't exactly the same as those printed in Trailblazer, but it's pretty close. I left off Trailblazer's Block option, because at the end of the day, it seemed kinda redunant with the Dodge option. Plus, I reworded everything slightly.
Combat Reactions can be taken for each round of combat. Rather than getting one per round, each character has a number of combat reactions equal to his attacks per round, i.e., a character with a Base Attack bonus of +11 would have three Combat reactions. For most Combat Reactions, you must threaten the opponent as per the standard Attack of Opportunity rules.
Combat reactions include the following:
- Aid Attack: if you announce your intention to aid an attack against an opponent whom you threaten, your ally will gain a +2 to his to-hit roll.
- Aid Defense: if you announce your intention to aid the defense of an ally from an opponent whom you threaten, your alley will gain a +2 to his AC from that attack.
- Dodge: if you announce your intention to dodge an opponent's attack, you gain a dodge bonus equal to ½ of your Base Attack Bonus (rounded down) against that one attack.
- Attack of Opportunity: you may take an attack of opportunity against an opponent who provokes one.