I'm finally starting to wilt to the repeated requests to reintroduce mana/magic points (MP was a stat in old versions of Dweller). I did a first stab at adding a generic energy stat currently only used by the wizard. The energy is reduced when casting spells and different spells have different cost. Some energy is regained after each turn and I'll have to reintroduce mana potions. Now that I think of it I actually believe this will be a good change that will add a lot of challenge to the way you play the wizard class.