It's not a new type of damage. What happens with the attack bonus of Perfect Shot is that it bypasses the target creature's sensitivity (unless the creature is immune to the original damage). Taking as example the current version of the eldritch wands (Perfect Shot +65 at range 4), their damage range is 85-105 fire damage which will be modified by the target creature's sensitivity to fire. However, when shot at 4 maps fields of distance, it will always cause an additional 65 fire damage. So, if used against a creature that is 20% strong to fire, at 4 maps fields of distance, these wands would hit 68-84 plus a fixed bonus of 65, i.e the final damage rage would be 133-149.