Spell Casting.

Using a mana Pool style. Each Spell Slot represents your mana pool. Level 1 spell slots are 1 Mana. Level 2 spell slots are 2 Mana. Etc. Combining all spell slots will equal out to your mana pool. Mana can be regained by Sleeping you regain half your mana on a "long rest" For each additional hour slept past you regain 1d4 mana. "Safe Rest" will regain all mana. Healing potions can be dedicated to your mana pool instead of your health. These Potions can not heal both nor be split between the two. Some Spell will be nerfed to keep the goal of a hardcore campaign. Spells such as Good Berry will not satisfice your appetite for the day. Create or Destroy water the water can not be consumed alone to quench your thirst, It can be used to create food for cooking or other activities. I.E Using create water to get water to make bread is able to be used for food.