Simple, but potent. I'm not a fan of mere mortals being able to manufacture indestructible items, but that is a minor flaw. More to the point when its worn it binds, hard, with the person's mind and while you could physically remove it, it would destroy the wearer.
Well, I would think that if fracking is able to create earthquakes, a hurricane with the huge movement of water, and subsequent adjustment of load could have an impact.
If the city had been built below sea-level - an insane idea on an island - then a hurricane could easily, and permanently flood it, for the water would have no place to go. Now, if the ground beneath the city was riddled with mines, its possible the flooding could add enough weight to collapse the mines and drop the city deeper.
Amethyst occurs in rocks with volcanic or igneous origin, so the ground beneath the city would be quite strong unless it was heavily mined, contained extensive open spaces (empty magma chambers) or both. Perhaps the island itself is an extinct volcano. Go to Comment
Perhaps it is nothing to do with roots. Real oaks count on squirrels to spread their acorns, so at first the squirrels happly spread the acorns. However, since they are not nutritious they eventually all starve. Once there are no squirrels nearby, the spreading stops unless happenstance - water, humans, spreads one to where squirrels can again carry out their duty:) Go to Comment
Interestingly, it has the feel of the really old Arthur tales, both good and bad, light on the whys. Some of the things Merlin did not seem to make sense with what was described in the tale.
So, it was a nice sword that resisted being turned to junk by the Wizard, and then to stop the battle (since it would I guess cause lots of collateral damage?) this third party sucked himself, the knight and the evil wizard into the blade?
Now the blade will draw energy to the trapped Evil Wizard, while the 'good' wizard will try and stop this by strengthening the wielder's tie to the weapon?