Summary
Gem arrives from Enroth fresh from the Succession Wars. She first helps the Clovergreen Militia and then aids a wizard's apprentice against the Necromancers of Deyja. (campaign description, taken from the game itself)
Scenarios
Clearing the Border
Win condition: defeat all enemies (only one in this case)
Loss condition: Gem is defeated in combat
After the Amulet
Win condition: acquire the Amulet of the Undertaker
Loss condition: either Gem, or Clancy is defeated in battle
Retrieving the Cowl
Win condition: bring Vampire's Cowl to the town of Leafhall
Loss condition: either Gem, or Clancy is defeated in combat; lose Vampire's Cowl
Driving for the Boots
Win condition: bring Dead Man's Boots to Gem's starting town
Loss condition: either Gem, or Clancy is defeated in battle; lose Dead Man's Boots