CRUCIBLE

a ceramic or metal container in which metals or other substances may be melted or subjected to very high temperatures.
“the crucible tipped and the mold filled with liquid metal”
  • a situation of severe trial, or in which different elements interact, leading to the creation of something new.
    “their relationship was forged in the crucible of war”
    A soulmate relationship is a crucible in which the partners can learn new skills together which they can then use in the larger world and other relationships.
    Example Larry and I are learning to communicate better with each other and already I am communicating better with others outside of our relationship using my new skills.