Convergence
The Convergence is a cosmological event which occurs only once every 5,000 years, when all the planets of the Nine Realms allign.
This allignment brings the wormholes which connect the Nine Realms closer together than they usually are, creating graviational anomolies and naturally occuring portals to appear at points closest to Yggdrasill.
During the First and Second Dark Elf Wars, Malekith the Accursed sought to use the naturally occuring portals to spread the power of the Aether through all Nine Realms simultaneously. During the first war he was stopped by Bor, and during the second by Jane Foster and Bor's grandson Thor.
Type
Metaphysical, Astral