Spell casting from Eragon

A way to do spell casting like it works in the Inheritance Cycle but in dnd 

Casting

you find that your can draw on your own strength and use magic. You have 1d4+your Constitution modifier Energy points (minimum of 1). You gain a level of exhaustion for every 3 Energy you spend, rounded down (spending 3 Energy is one level, while 6 energy would be 2 levels. 2 or less energy would be p levels of exhaustion). You may do anything within the bonds of what you can create and manipulate, at DM's agreement, however, the DM can adjust costs as needed (Example, it could cost extra for ranged fire attack or an exploding fire attack or both, though both would cost the most. You could create a wave of fire that could cost a lot of Energy, perhaps more than an exploding ranged fire attack (i.e. a fireball)). For all intensive purposes, effects preformed through these means are spells and are treated as such in all occasions. Your caster spell save DC= 8+Charisma modifier+proficiency bonus. Your Caster spell attack modifier= Charisma modifier+proficiency bonus. You recover 1d4 Energy aftertaking a short rest and recover all your Energy after taking a long rest. Concentration may be required (if spell has a duration and is not "self-sustaining" for that duration (Example: Light is a "self-sustaining" spell, Levitate requires concentration). Concentration spells may not require much Energy at one time, but can cost extra Energy over time. (Note: Process of deciding ability functions/costs are generally as follows:

1. Spellcaster decides on what they want to happen. (Example: Jake wants to create a whip of fire.)
2. DM decides if they will allow effects, then decide on cost. (Example: DM allows Jake's whip at a cost of 1 Energy each turn. The whip has a 10 feet range and does 1d4 fire damage.)
3. Player make adjustments, with DM adjusting cost. (Example: Jake increases range by 5 feet, DM adds 1 Energy to cost. Jake also increases die type to d6 (DM adds 1 Energy to cost) and adds a second die (DM adds another Energy to cost)).
4. Energy is paid, effect is carried out, and levels of exhaustion are gained, if applicable. (Example: Jake pays 4 Energy. His character creates a whip of fire that has a range of 15 feet and does 2d6 fire damage. They gain one level of exhaustion)

(NOTES FOR DMs: A good way to determine Energy cost is to do the following:

You have the following abilities:

Pyrokinesis

You can manipulate and create fire. You may describe any effect that focuses on fire (creating a campfire, shooting a fireball, sending a fire wave, even spontaneous combustion, ANYTHING with DM's agreement, but fire must be the primary focus, no levitating objects and causing them to catch on fire, just catching them on fire). Spells with cost more as their effects become more potent (Lighting a campfire would cost 1 Energy, while spontaneous combustion would probably cost about 7-8 Energy and only effect one creature that has less than 50 hit points, but probably do 5d10 fire damage on a failed Constitution saving throw or half that on a success).

Magic Blast

You can use energy to create a blast of magic. You may spend 1 energy point to create a small ball of energy that does 1d6 force damage that has a range of 60 ft away from you. This can be modified to add more damage dice, increase die type, increase range, even change damage type, but each modification would increase Energy cost (most previously mentioned effects would increase cost by 1, while changing damage type would probably cost 2 Energy).

Young Caster

At level 6, you have improved, but still have a long way go. Increase your Energy by 1d4+your current Constitution modifier (minimum of 1) (your Energy maximum does not change after this, unless an ability says so). You gain the following abilities:

Air Manipulation

You have gained some control over the air. You may describe any effect that focuses on air (such as a gust of wind, a cushion or wall of air, or even use air to expand and break or compress and squeeze something). (It would cost one Energy to create a gust of wind to blow a sail, but maybe 3 Energy to crush something with air and that crushing may need a Constitution saving throw to determine if is works).

Darkness and Light

You can control darkness and light. You can change the light level of an area with a 60ft radius around you (this could cost 5 Energy per level changed (bright to dim to darkness or vice versa)).

Adept Caster

At level 10, you are familiar with your abilities, if not overly skillful. Your Energy increases by 1d4+your current Constitution modifier (minimum of 1) (this does not change unless an ability says so). You now gain a level of exhaustion for every 5 Energy you spend, rounded down . You also gain the ability to store Energy in gemstones. A gemstone must be worth at least 100gp to be able to store Energy. You can store 2 Energy for every 50gp a gemstone is worth. You can store and take Energy from the gemstone at will, this does not change the gemstone in anyway. You can sense if a gemstone has Energy, and how much it has, as long as you can hold it (DM may grant gemstones containing Energy as treasure, but they should be rare to find). You can draw from these gemstones as long as they are on your person to either cast a spell or regain Energy points. Using Energy from gemstones does not grant levels of exhaustion, but storing Energy in them can. If you store Energy in a gemstone, you must wait 1 minute before you can do so again. You have the following abilities:

Skilled Caster

At level 14, you have become very skilled with your powers. You increase your Energy by 1d4+your current Constitution modifier (minimum of 1) (is does not change unless an ability says otherwise). You gain the following abilities:

Earth Command

You have gained sufficient power to command earth. You may describe any effect that focuses on earth (flinging a boulder at someone, creating a wall of rock, creating quicksand (or quick-mud), and even encase a creature in stone). (Moving a boulder might cost 1 Energy per turn that they move it, while encasing a creature in stone might cost 7 Energy and include a Dexterity saving throw or they became essentially petrified.)

Healing

You have discovered that you can make any injury be healed, aside from death. You can heal a person as long as you can touch the injury. You can heal 1d8 hit points at the cost of 1 Energy. You may increase the number of dice (1d8 to 2d8, etc.) or die type (d8 to d10 to d12) for each extra Energy you spend.

Master Caster

At level 18, you can make use of abilities that only masters use. You increase your Energy by 1d4+your current Constitution modifier (minimum of 1) (this cannot change from this point forward). You now gain a level of exhaustion for every 6 Enetgy you spend, rounded down. You gain the following abilities:

Time Mastery

You have mastered Time itself. You may describe any effect that focuses on time (slow time, turn back time, even grant yourself extra turns). (Effects like these would cost anywhere from 7 to 10 Energy).

Lightning Cast

You discover that you now can command lightning. You may describe any effect that focuses on lightning (shock something, strike something with lightning, or even create a thunderstorm). (Shocking something would cost 1 Energy, while causing a thunderstorm might cost 5 energy and effect a 20ft area and strike all creatures within eah round for 1d6 lightning damage and last for 1d4 rounds.)