If you choose to include a spell card in your deck, Harsk doesn't gain anything but the card. You wouldn't have to banish the spell at the end of the scenario, but you would have to banish it after you use it.
Fortunately, once you choose a role (either Sniper or Tracker) you can use a Power Feat to gain the skill Divine: Wisdom +1. If you do, you won't have to banish spells with the Divine trait.