There is one other explanation that works with the text and visuals. Auru tells us that the Gerudo desert "holds the cursed mirror and the malice of the doomed inmates", which he later says he found out from the Sages. Not only does this explain the "evil power" that the Twilight Mirror possesses, but we also know that Ganondorf was in the presence of the Twilight Mirror when he became empowered and the Triforce of Power resonated.
Before you begin shouting that the Triforce of Power came to Ganondorf in that scene to empower him, which is why the Sages were surprised, this isn't necessarily the case. Three reasons for this:
1) "Divine prank" means "prank in relation to the divine", not necessarily "prank caused by the divine". The Triforce is a "divine relic" so the term could be referring to that he possesses the Triforce; nothing to with the gods.
2) The gods have opposed darkness throughout the game series; they ordered the Sages to protect the Mirror, they commanded the Sages to forge the Master Sword, their power infused the Master Sword with it's ability to repel evil, etc. To grant evil a piece of the Triforce therefore goes against everything that they have fought for in the game series, and makes no sense.
Furthermore, when Link and Midna are about to enter the Twilight Realm, the Sages appear and apologise to Link for their own carelessness. If the gods were responsible for Ganondorf's empowerment, then the Sages would attribute the blame to the gods, not to themselves.
3) The Sages look shocked when Ganondorf shows the resonating ToP, but were they surprised in discovering that Ganondorf possessed the ToP, or that he was empowered by it? If you read the text carefully, nothing suggests that they had no knowledge of Ganondorf possessing the ToP, but if he could be subdued while possessing it, then there would be no potential threat. The surprise would have come from finding that Ganondorf remained a potential threat. Let me explain this further:
Ganondorf possessed evil magic before and after he took the ToP, which suggests that the ToP is empowering his evil magic; not simply Ganondorf. So what if Ganondorf was separated from the evil magic that he possessed (obviously not all of it, because that would kill him)? Would the ToP be able to empower anything if Ganondorf had no evil magic to empower? Without magic, the ToP can do nothing so the Sages don't consider Ganondorf a threat.
However, if the malice in the Twilight Mirror is able to restore Ganondorf's evil magic to him, then the ToP can empower that magic, causing it to resonate with power. This is when Ganondorf is sent to the Twilight Realm, where he establishes Zant as his pawn and uses him to merge the Light World and Twilight Realm together.
I won't deny there's speculation in this theory, but when you remember that TWW also showed Ganondorf separated from his evil magic in Old Hyrule and forced to regain his strength on the surface, it is not such a ridiculous concept.
Edited by jhurvid, 19 January 2007 - 03:23 PM.