SMOOSH JUICE
New Spell – Dragonkiller

Astra smiled, the light catching on the scarred side of her face, making it seem quite horrific for just a second. “I have it,” she held up a broken black dragon scale.
“It is his?” asked Tallisyn.
“Do you know any other dragon that has laired here?” asked Astra.
Tallisyn thought to themself for a moment before responding, “No, I don’t.”
“Then I think we are safe in thinking it belongs to him. No one outside of our group knows of our plan, so not one should have planted a false scale.”
Dragonkiller
This spell was made, as you would guess, to kill dragons. A transmuter who had nearly been killed by the acid-breath weapon of a dragon and has vowed to kill those dragons who threaten destruction and harm to people. While designed to defeat rogue dragons, any weapon can be turned to ill ends and this spell is no different.
Dragonkiller
6th-level Transmutation | Wizard
Range: 120 feet
Casting Time: 1 action
Duration: Concentration, up to 1 minute
Components: V, S, M (multiple dragon scales)
This spell draws upon the elemental nature of the dragon and turns it back upon itself, transmuting the flesh around the dragon’s heart into that of an inimical element, causing great distress and damage to the dragon affected.
This spell can only target dragons and draconic creatures, attempting to use it against any other sort of being just fizzles out. The dragon targeted by the spell takes 5d8 of a damage type they are vulnerable to, or, if they are not vulnerable to any type of damage, then a damage type they lack immunity or resistance against. Once the damage type is set, it remains for the duration of the spell.
The target makes a Charisma saving throw: On a successful saving throw they take half damage. On a failure, they take the full damage and suffer -1d4 to their to hit and ability rolls until the end of their next round.
The damage, and need for saving throws, continues each round until the spell ends either by running out of duration, dismissal by the caster, or the caster losing concentration.
If the caster has a scale (or other piece) from the targeted dragon, the dragon makes its saving throws against this spell at disadvanage and the caster gains advantage on checks to maintain concentration. This does consume the piece used to create the tie at the end of the casting.
At higher levels: Each level about 6th that it is cast at, increases the damage by 1d8. If cast at 7th level, the target suffers disadvanage on ability checks until the end of its next turn on a failed save (instead of the -1d4), at 8th, disadvantage is also applied to hit rolls on a failed save (again, replacing the -1d4) and at 9th level, the dragon suffers a =1d4 to saving throws until the end of it next turn on a failed saving throw against the spell.
Notes: I created this spell for my character Astra uth Terra from our Dragonlance campaign. Not that I will ever get to use it as our campaign is coming to a close. But as she is a transmuter with a hatred of evil dragons, I wanted to make a dragon killing transmutation spell just for her.
Someone in the Sea of Stars would have developed something similar, after all, there are people there who really hate dragons.
Image Dragon Killer by Pepe-Navarro, DeviantArt, used under a Creative Commons Attribution-NonCommercial-No Derivatives Works 3.0 License.