There have been a lot of items introduced with the Timeless Isle and all those new rare mobs running around everywhere on Pandaria, and lot’s of them are not only fun to use – they are actually useful in some kind or the other. For example, there is the Cursed Swabby Helmet, which not only turns you into an ape with a diving helmet (yeah, I know they’re Hozen, but they’re rather ape-like after all o_o), but also gives you a nice buff that increases your swimming speed and grants breathing under water:
That alone is neat enough already, but on top of that the Aqua Jewel is usable when in Hozen form already and applies its buff over it, resulting in a ghostly look. So if you ever need a ghost ape for roleplay purposes – at least the look of it applies to transformations like this one, and I’m assuming that the speed buff works as well, though I’m not entirely sure if stacks with the one of the helmet – will have to try this out at some point.
Additionally, there are other transformations or extras that get altered when using the Jewel, like the Druid and Priest Statue Set (the green glow becomes rather ghostly too, and way harder to see than normally), the Goblin Dragon Gun, Mark II (the gun looks as see-through as the user, and the flames are pretty much invisible) and also on the changed shape of the Elixir of Wandering Spirits (and makes you look like the spirit of a Pandaren for real – I guess that could be useful for roleplay purposes as well eventually).
And not to forget, besides full transformations it also works on stuff that applies to the character like Ken-Ken’s Mask (This one makes it almost look like the face disappeared instead of showing a mask – though I guess it would have been cool to have it floating around with its normal look instead) and on mounts! And that’s only what I tried so far, maybe there are even better ways to utilize the spooky effect. Even though Halloween is over already.^^