If there is nowhere to replace a desorcelled Hero, because of blocking elements or terrain, where is he placed?
If the Hero is supposed to appear adjacent to the enemy stronghold on the base edge, then place him adjacent to the stronghold as close to the base edge as possible. If there is no space at all adjacent to the stronghold, then the Hero cannot be placed. If the Hero is to be placed in the centre of a base edge then place him as close to the centre as possible.