If you play an event that puts a card into play during an engagement, can you put that card in the engagement as a participant? Rules just say play area.

videinfra said:

Not unless it says it comes into play as a participating unit on your side.

If you're the defender in an engagement, there is a player action window after attackers are declared and before defenders are declared. You could put it into play at that time, and then declare it as a defender during the declare defenders step.