Included in the shipping box with Wun-Dar (and Evil-Lyn, since they came together) for those who subscribed to the full year of "Club Eternia" was a free bonus item, a poster featuring a map of Eternia:
Ancient Planet of Mystery and Power
Gifted with the Wisdom of Ages, the Elders of Grayskull secretly knew that the twin warriors of the Great Prophecy would one day be born on their planet. Therefore, they made a secret bargain with Trolla. In return for keeping the Power Sword of He on Eternia, one member of the Elders was to join the Cosmic Enforcers, beings tasked with maintaining neutrality throughout the Universe. The sword was then split in two and hidden, awaiting a time when worthy heirs would reclaim it, channeling its power and their wisdom to transform into heroic Masters of the Universe, fulfilling the prophecy to defeat the Horde Empire and restore peace to the Universe.
A lot of intrigue - in the "political machinations" sense – in this one. It seems the Elders of Grayskull "secretly" know that twin warriors will someday be born on Eternia. So they make a deal with the Trollan Overlords of the Timeless Dimension (or whatever it's called), trading Zodac for the Sword of He - which, need I point out, is just one sword, not two.
Let's be honest here: does this seem like a fair trade? Were the Trollans that short on good candidates for Cosmic Enforcers?
Besides, the Trollans gave He-Ro the Sword of He, who gave it to King Grayskull when he died, who gave it to the Elders. It's a pretty douche move for the Trollans to suddenly lay claim on a Sword they haven't had anything to do with for years. But I suppose Overlords tend to be douches, whether they're good or evil.
I assume the reason the sword was split in two was to help make it easier to hide from evil hands. But who did the splitting? The Trollans, the Elders, the Goddess, or someone else entirely? Also, maybe this would have been the time to ask the Trollans to split the sword into two whole Swords, one for each twin, rather than the Sorceress having to "clone" (bleh) it later. Just seems to be a general lack of planning ahead, despite obvious potential problems.
Finally, it seems the twins are prophesied to defeat the Horde Empire specifically. Very Star Wars, that, though the Horde Empire was always a vague ripoff of the Empire and MOTU borrowed a lot from SW over the years. It does seem to demote the Snake Men a bit, though.