I've changed it a bit now, but the main concept was that this was more a McGuffin level of weapon for when the players are at a high enough level that it's more balanced - I think the aging effect handles like a vorpal effect, in that it can insta-kill. But by limiting it to non-magic users, and effectively just warriors, it removes the worst abuse (de-aging for an infinite number of wishes) and makes the de-aging more of a threat.
I was looking more for a very strong magic item - after all, it is made from a dragon's powers combined with the powers of the mage who killed him! I prefer a fast aging process because it instills a deep fear in people - imagine being a young elven fighter, who gets stabbed once by an assassin and is suddenly old and grey!
The problem with slower aging is that it's not as useful in a straight-up fight. An insta-kill on most foes when you crit is about the same level of power as a vorpal weapon, and an issue players might hit is that it will actually make dragons stronger! A fitting final act by a powerful dragon, wouldn't you agree? :) Go to Comment
Instead of summoning something when failing, it could trigger a number of traps (the floor falling away, and a pit opening up; a number of arrows/spears being fired into the room; or even spikes coming out of the floor). Go to Comment
In the Temple Square of The City, where the nine Greater Gods have their houses of worship, a sudden flash of light blinds (perhaps permanently) all those who are nearby. When the light has faded, a tiny, naked baby is lying in the doorway of each Temple. The Gods, it seems, have come into the world - but why?