You may have an additional hero in play.
Heroes' Hall only does anything when you want to play a hero. You can determine how many heroes you can play like so: - If you have an active Tech 3 building, or you have an active Tech 2 building and an active Heroes' Hall, you can play all 3 heroes. - If you have an active Tech 2 building or an active Heroes' Hall, you can play 2 heroes. - Otherwise, you can play only 1 hero. — sharpo, 06/16/16
Losing Heroes' Hall won't cause any of your heroes to leave play. — sharpo, 06/16/16