When you attack with a Grenades that you crafted, you can spend 1 charge of either Mana Flux or Aether Flux to gain a +2 Bonus to your attack roll.
When you attack with a Grenade, you can designate a number of creatures equal to the number of Proficiency Boosts you have in Aethertech Lore. Those creatures are immune to the effects of that specific Grenade attack until the start of your next turn.