Maskelyne's Conservation

The Wizard Maskelyne was one of the foremost experts on Thaumomancy, also know as "Magic-Magic". Thaumomancy is the field of magical research that develops spells which manipulate other spells; arguably the crowning achievement of this field is the famous Counterspell, which the Abjuration school has unfortunately since claimed as its own. Thaumomancy has advanced Wizardly knowledge by leaps and bounds, and Maskelyne was one of its pioneers.

His signature invention, his Conservation, was first invented to win a bet; only after it was completed did it become clear how useful it could be. Many Wizard schools teach their students to trigger additional effects when they expend significant resources; Maskelyne's Conservation presented a way for those Wizards to trigger those additional effects efficiently without needing to expend unnecessary resources.

In a rare case of Wizards developing a technique before the so-called 'intuitive casters' of Sorcerers and Warlocks, after the invention of the Conservation, these intuitive casters started spontaneously developing an ability that was functionally identical. This has led to the fringe hypothesis that the study of Thaumomancy can have effects on the very fabric of magic itself, which, naturally, has only made Wizards more eager to investigate it.

-Reginald Kline, "Thaumomancy: Wizards' Feat or Folly?"

Maskelyne's Conservation

3rd level evocation

Casting Time: 1 bonus action

Range: Self

Components: SV

Duration: Instantaneous

Classes: Sorcerer, Warlock, Wizard

By casting this spell, you generate just enough energy to trigger minor magical effects, while wasting minimal magical power.

When you cast this spell, you create an extra spell slot of 2nd level or lower. The spell slot lasts until you complete a long rest or until you use it.

At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, you can create a spell slot equal to the level at which this spell is cast minus one. Alternatively, you can change the school of magic this spell belongs to, and create a spell slot equal to the level at which this spell is cast minus two.