Archery
Archery is a secondary skill, that increases the dealt damage of ranged attacks including ballista. Orrin the Knight is the only hero to specialize in Archery.
Artifacts affecting this skill:
Heroes with Archery as a starting skill
Ivor starts with Basic Archery.
Jenova starts with Advanced Archery.
Discussion
Archery is a secondary skill with two sides. Is almost useless if a hero has only few (weak) ranged units. On the other hand, it may be even better than Offense, which only gives 30% increse to melee damage, if a hero manages to muster strong ranged units like Titans and Cyclops Kings. From the faction Tower and Dungeon heroes are perhaps the advisable candidates to choose Archery because of the powerful ranged units. Archery combined with the artifact Golden Bow is an effective combination, not to mention the combination artifact Bow of the Sharpshooter in Shadow of Death.