True Evocation

This spell was inspired by the Witch Bolt spell, and altered by a master of the Evocation school to become a powerful weapon for a wizard's arsenal that offered both raw power and versatility. It was only taught to a handful of highly trusted colleagues, and those outside the School of Evocation do not know it even exists.

After spending a full round summoning the energy required, the caster's next round unleashes a punishing barrage of lightning bolts, gouts of flame, or spear-sized icicles, dealing 6d6 damage (lightning, fire or cold, respectively) per round for up to 1 minute, or until the caster's concentration is broken. If cast at 8th level or higher, the damage dice becomes 8d8. This damage applies to the target and the area within 15 feet of it. Target must make a save vs spell (DC equal to the caster's spell attack) or take full damage; successful saves mitigate damage by half.

If cast at 9th-level spell slot, the damage dice becomes 10d10. Additionally, the caster may elect to forego the concentration effect and deal 5d10 for all three elements at once, for a total of 15d10 damage.

The sheer strength of this spell does come with drawbacks, however. Due to the demands of channeling and safely controlling such extreme power, the caster is rooted in place for the duration of the spell and can take no other action (regardless of abilities or feats to the contrary). Once the spell is finished, the caster must spend 2 rounds recovering from the mental strain of maintaining such high concentration before casting again. Additionally, this spell may only be cast once per long rest.

This spell is only available to wizards of 14th level or higher who specialize in Evocation magic, and is not found on a scroll. Learning it will require two weeks of training under the tutelage of a master Evoker, and permanently sacrificing 2 spell slots of 7th level or above. The price is high, but not to those who yearn for unspeakable power or tightly-guarded secrets.