The Eight Elemental Blades...

In The Galactic Conquest there are 13 Lords and Avatars. Eight of them required constructs to keep them in sentient existence, had they not created these items they would fade in to a force of nature. The other five did not need constructs but ended up creating their own to ensure universal stability. The eight beings that needed constructs were the lords and avatars of light and darkness, fire and water, earth and electricity; wind and ice. Each bladed was forged out of the creation of the avatars. The sword does the respective wielder's bidding, but can only harm the wielder. 

When the avatars were created to stabilize the comprised lords, the blades and constructs were also crafted to stabilize the avatars themselves, or at least for the eight elemental avatars, least they too would leak into oblivion. And so the blades were created to act as both a seal (to prevent them from flowing out into a force of nature) and a vent (to allow the build of raw energy to be expelled in a controlled manner).

On top of the constructs acting as their medium for power and a fail-safe kill-switch, if the eight blades were combined they would bring balance to the eight elements should they become chaotically displaced (it should be noted that the eight and only the eight should be combined and not one extra).

There were two other blades crafted, the Kronosbane (Blade of Time) and the Gemátos Akyró̱soun (Blade of Space). The Kronosbane cannot ever be combined with the other blades since time cannot be undone and is ever flowing. The Gemátos Akyró̱soun on the other hand can be combined with any other blade, allowing the respective avatar to [temporarily] have an infinite amount of power. This is usually done to combat the flawed doings of Chaos; in a sense it creates a Blade of Chaos (of course augmented with the element).

This is exactly why the eight blades should nevar be combined with the Gemátos Akyró̱soun (the combination of the eight equals the power of a lord, adding the Gemátos Akyró̱soun would create a Diafthorá (Blade of Corruption), or a construct for the Corruption Lord [granting him a window, or a door, to this dimension and allowing him to further taint and corrupt what he already made degenerate and set for an eternal decay]).