RulingHall of Heroes (rules 1.0–1.4)
Expansion card questions: How does the timing for Expert Defense work?
Question
How does the timing for Expert Defense work?
Answer
You must exhaust your hero to defend in order to boost its DEF by 3 for that attack. Also, you must play it immediately after declaring your hero as a defender, which occurs before boost cards are revealed.
-Caleb