The Crux of Eternity appears as a crystal cross large enough to be held in one hand. Manufactured by the now-dead god Sorg during the Dawn War, the Crux of Eternity — also known as Ydinikuisuuden — was a masterweapon designed to channel the power of the gods. (Interested parties may wish to read about the creation of Ydinikuisuuden.) It was so feared that the primordials forged the Doom of Divinity, Godenschemering, in retaliation, although it was too late; the gods managed to defeat, exile, or imprison the primordials, forming Creation as we know it today.
As the Crux is so potent, it was hidden away somewhere where mortals and primordials could not find it. (Its resting place is unknown, although most people suspect it resides in Sorg's tomb, wherever that may be.)
The Crux's powers are unknown — no one in living memory has even seen it, much less used it — although there is some speculation as to what it might be able to do:
- It acts as an implement for channeling holy power. In D&D 4e, it's almost assuredly a +6 holy implement, usable with Divine powers; it's possible it can be used as an implement for other power sources, as well. In other editions, it might maximize spells, or make saving throws against spells cast with it more difficult, or possibly even grant additional spell slots or spell uses. (It doesn't seem out of the question that the Crux might allow its user access to any available spell, for example.) Whatever it does, it makes spells — particularly divine spells — more efficient. It probably also acts as a spell catalyst, meaning that spells don't require material components to cast as long as the Crux is involved.
- Likewise in D&D 4e, it is thought to maximize rituals, amplifying their effects and possibly obviating the material component costs of rituals. This is related to its "maximizing spell function," above.
- It seems logical that any attacks channeled through the Crux would deal extra damage to elemental beings, given its pedigree as an artifact designed to slay primordials.
- Some theorists who think it maximizes magic suspect it doesn't actually affect spell-casting, instead granting wishes, a potent magic long-thought absent from magic items on Khaldun. (There's a long-standing rumor that a ring of three wishes was buried in the Tomb of Theronna Onyxarm, although no one knows if that's true or not. For that matter, scholars aren't even entirely certain where her tomb might be.) If this is true, then the Crux of Eternity's legendary reputation is well-deserved.
Of course, if the Crux were found, it would likely require lifetimes of study to successfully use, as its activation methods are probably just as well-hidden as the Ydinikuisuuden itself.