  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, in particular, we consider the Morse Index analysis and 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.
