Notes:

Long story short: Gullveig mothers Heiðr right after winning ands yeets her into the distant past with no memories so she can become her present self (Seiðr)'s sister, all so Heiðr can latter become the trigger to cause Seiðr to evolve into Gullveig Pokemon-style.

And in the meantime, she also reverts herself into her baby form (Kvasir) and yeets herself into the distant past also with no memories so she can later become Seiðr, thus creating a time-loop where Gullveig more or less exists as a paradox who can't be rid of conventionally.

…Confused yet?