Spell: Lyra's Burning Pants

[Skijarama]

So, during a session I jokingly came up with a spell, but we all liked the idea so much that I decided to write it up.

Lyra's Burning Pants (Wizard, Warlock, Sorcerer, Bard)
3rd Level Evocation

Casting Time: 1 Action
Range: 30 Feet.
Components: Verbal, Somatic.
Duration: Concentration, up to 10 minutes.

You target a single creature within range and mark it with magical energies. The target may choose to make a Charisma Saving Throw to resist the effects. As long as the spell is in effect, any time the target willfully and knowingly tells a lie, their lower body immediately flickers with fire, dealing 1d6 Fire damage.

At Higher Levels: When you cast this spell using a spell slot above 3rd level, you may increase the damage dealt by an additional 1d6 for each level above 3rd.

[Composer99]

So, during a session I jokingly came up with a spell, but we all liked the idea so much that I decided to write it up.

Lyra's Burning Pants (Wizard, Warlock, Sorcerer, Bard)
3rd Level Evocation

Casting Time: 1 Action
Range: 30 Feet.
Components: Verbal, Somatic.
Duration: Concentration, up to 10 minutes.

You target a single creature within range and mark it with magical energies. The target may choose to make a Charisma Saving Throw to resist the effects. As long as the spell is in effect, any time the target willfully and knowingly tells a lie, their lower body immediately flickers with fire, dealing 1d6 Fire damage.

At Higher Levels: When you cast this spell using a spell slot above 3rd level, you may increase the damage dealt by an additional 1d6 for each level above 3rd.

I like the humour. It's definitely a niche spell - not overpowered in any respect that I can see. Rather the opposite: with its AoE and non-concentration duration and lower level, zone of truth is strictly speaking a better spell for the niche of "truth-finding", and this spell doesn't work in combat. You could probably make this 2nd level and it still would be a weaker option. I wouldn't make it 1st level, though.

A quibble about the wording: when a 5e spell forces a saving throw, spell descriptions invariably use the term, "On a failed save" somewhere when discussing the spell effects, even though that's usually implicit from the fact that the spell forced a save in the first place.