Pandora's Spell

In a world where everything is dying Harry is given one choice:
º Go back in time to undo the damage by doing a Sacrifice Ritual to save himself and his children,
or
º Stay in the horror that was this new world and end up dying by the end of the month.

Once in the past can he really go against everything he believes and join the Wizard he once defeated?

Cover by RiddleSnape(AO3)/@S1L6Moon9(WP)