Unbreakable Vow

This spell creates a binding magical contract cast between two parties, that if broken by either party, will result in imminent death of whoever broke the contract. 

The two parties must be standing opposite each other and clasping each others right hands. Then, each will ask a vow to the other, whereupon each time the second accepts a term, a magical aura will surround both hands. A magical branding mark will appear on both parties hands and can't be dispelled or removed until both vows are complete or by the effect of a wish.

The contract brand also appears if the vow has been made on another person, for example if you swear on your brother the mark will apear on him or if you swear with your life, each time one of the parties that hasn't complete their vow takes damage, the other part take half the damage.

The spell ends if both parties agree.