Contract of the Green Coven

Bound Together. This contract can be signed by three individuals to bind them together. Each individual has to sign the contract willingly with their own name. Then, the three have to simultaneously speak a command word at midnight while touching the contract. When this final step is completed, the scroll vanishes and the individuals are bound together.
  While bound together, all individuals gain the following benefits while they are all within 45ft. of each other. They gain a +1 bonus to their AC and to all spell attack rolls. Additionally, they can breathe air and water and gain proficiency in the Sylvan language.
  If one of the individuals dies, the three individuals are no longer bound together. When this happens, the remaining two individuals instantly take 5d8 Psychic damage. If this damage reduces them to 0 hit points, they die outright. Other than an individual dying, the contract cannot be broken by anything short of a Wish spell, or by the entity that originally created this contract.