Inferno

In the trilogy's finale, reality itself has come undone: normal space-time survives only aboard the Defiant and a lone Klingon ship, adrift while the Prophets and Pah-wraiths wage a cosmic war around them. To restore existence, Sisko must return to Deep Space 9 at one of two moments in its history, and the price of undoing the damage may be his own future. The concluding novel of the Millennium trilogy.