In Star Trek VI: The Undiscovered Country, the Praxis explosion begins the Federation's peace process with the Klingons.
Praxis is a major Klingon moon and an important source of energy for the Klingon Empire. Its catastrophic destruction causes an environmental crisis around Qo'noS and leaves the empire facing severe economic and political pressure.
The disaster forces Chancellor Gorkon to seek peace with the United Federation of Planets. He compares the situation to a historic turning point and proposes negotiations, but enemies on both sides try to sabotage the talks because they profit from the long-standing conflict.
The USS Enterprise-A is assigned to escort Gorkon to the negotiations. After Gorkon is assassinated, Captain Kirk is blamed and imprisoned, while Spock and other allies uncover the conspiracy. The film ends with the signing of the Khitomer Accords, establishing a major change in Federation-Klingon relations.