Question

If tachyons exist, what would they do to spacetime?

Answer 1

Mass (Positive) bends space-time generating gravity. If Tachyons are supposed to have imaginary mass, what would they do to spacetime (if they do exist).

Answer 2

 an imaginary mass accelerates toward a real mass, but a real mass accelerates away from an imaginary mass, so they are both accelerated along the axis passing between them. The other part of the question is how something going faster than light can be localized to anywhere at all.