In this work , we consider time-dependent dark energy star models , with an evolving parameter \omega crossing the phantom divide , \omega = -1 . Once in the phantom regime , the null energy condition is violated , which physically implies that the negative radial pressure exceeds the energy density . Therefore , an enormous negative pressure in the center may , in principle , imply a topology change , consequently opening up a tunnel and converting the dark energy star into a wormhole . The criteria for this topology change are discussed and , in particular , we consider a Casimir energy approach involving quasi-local energy difference calculations that may reflect or measure the occurrence of a topology change . We denote these exotic geometries consisting of dark energy stars ( in the phantom regime ) and phantom wormholes as phantom stars . The final product of this topological change , namely , phantom wormholes , have far-reaching physical and cosmological implications , as in addition to being used for interstellar shortcuts , an absurdly advanced civilization may manipulate these geometries to induce closed timelike curves , consequently violating causality .