Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.

Heroic abilities will resolve before the spell that caused them to trigger.

Heroic abilities won’t trigger when a copy of a spell is created on the stack or when a spell’s targets are changed to include a creature with a heroic ability.

If Mindreaver leaves the battlefield, and later another Mindreaver enters the battlefield, it is a new object (even if the two were represented by the same card). The last ability of the second Mindreaver doesn’t refer to any cards exiled with the first one.

The cards are exiled face up. All players can look at them.