Feast is a food item from the base set that is applied to every hero revealed when a player enters the dungeon, granting each one a bonus of +3 Strength as well as +1 Physical Attack. A total of four heroes would therefore add a total bonus of +4 to the Total Attack Value.
Destroying this food for card effects, such as the Thyrian/Outlands heroes, prevents any of its own effects from taking place - the Strength / Physical Attack bonuses are lost.