Reactions cost 1 action and are performed when it is not your turn. A hero can perform each reaction no more than 1/round, and they will start their turn with fewer actions. The reactions are:
Defend
Reduce damage from any single attack by your Armor whenever you use this reaction. At the GM’s discretion, some damage may not be avoidable (e.g., psychic damage, or some areas of effect).
Interpose
If a creature within 2 spaces would be struck with an attack, you can push them out of the way and become the new target of the attack. You enter their space and move them to an adjacent space of your choice.
Interpose AND Defend?
Yes! As long as you have enough actions to spend, you can Interpose and Defend at the same time. However, you won’t be able to do either reaction again until your next turn is over since each of those is limited to 1/round.
Opportunity Attack
A melee attack made with disadvantage against an adjacent enemy as it willingly moves away. Monsters do not make opportunity attacks, only heroes can.
Help
Grant an ally advantage on a roll if you can reasonably explain to the GM how you could help in a given situation (limit: one Help reaction for each roll). The GM may call for a skill check or grant advantage automatically, depending on how good the idea is.
Teamwork!
Help as a Heroic Reaction is a fantastic way to bring teamwork, role-playing, and creativity into a combat encounter. Did your buddy fail? Maybe not! Think quickly and see if you can help them succeed.