Promise

The "Promise" spell is a powerful transmutation spell. Created by the White Dragon named Aenophentari in ancient times. 
It is a little known spell, with few knowing about it and even fewer knowing how to cast it successfully. 
The spell binds someone to a promise or oath that they make to the caster, with disastrous results if they break that promise or oath...

Effect

The immediate effect is effectively nothing. However, if at anytime someone breaks the promise they made to the spell caster they will be subject to a "penalty." This penalty generally depends on the oath or promise itself. If someone promises to "Not steal a cookie from the cookie jar" the effect of the spell is usually minor like a burning sensation in the persons head or hands. But if someone promises to "Keep your secrets upon pain of death" the promise spell will instantly kill them, or worse.

Side/Secondary Effects

Some who break the spell in a way that kills them have been known to come back from death as wraiths, ghouls, or worse due to the amount of magical energy imbued into them.