Exhaustive Casting

Through research and experimentation, you have learned to cast spells using an expended Spell Slot.  Spells cast in such a way come at a high, possibly life-threatening cost.

Benefits:

• The caster casts spells using an expended spell slot as if it was an unused slot and is still bound to all the usual rules surrounding the casting of spells.
• The spell works as normal and may be affected by class features, such as Metamagic, as per the rules.
• The expended slot may be used to upcast a lower level spell following the rules given in the spell's description.  Spells which do not expend a Spell Slot can use this feat to upcast that spell if they are normally allowed to be cast using a higher level slot but the Caster will suffer the Cost for using an expended spell slot as descibed below.

The Cost:

• The Caster immediately gains +1 Level of Exhaustion.  This will affect the following...
• The Caster must also attempt a Wisdom DC Save of 8 + the expended spell slot lvl or suffer Psychic Damage equal to 3x the level of the expended spell slot.  Successful saves take half of that damge.  All rules regarding Resistance, Immunity and Vulnerability apply normally to this damage.

Example: During a battle. a wizard has expended all his 3rd level spell slots but remains hard pressed by many foes.  Resigned, he decides to cast using an expended 3rd level slot and hurls a Fireball at his foes.  He immediately suffers +1 Exhaustion (his only level at the moment) and must attempt a Wisdom DC 11 (8 base, +3 for using a 3rd level expended slot) with the -2 penalty on his D20 test for having a level of Exhaustion.  He will suffer 9 (3x the expended 3rd level spell slot) psychic damage on a fail and 4 on a success.