Part 96: Bonus Update 51.5: Elemental PlanesBonus Update 51.5: Elemental Planes
If you don't want to mess around with the elemental tests, they're completely optional: the only thing you have to do on any of the elemental planes is find the sleeper, awaken him and get out.
Most of the other three elemental planes' hintbook entries are just copy-pasted with the names of the elements changed. I've only included the parts that are substantially different.
That note about earthquakes in the Elemental Plane of Earth's description isn't just flavour text, by the way. When you walk on certain parts of that plane, there's a chance the whole party will take a small amount of physical damage. Something similar can happen in the Elemental Plane of Air, but with electrical damage instead of physical. I didn't mention it in the main update because I couldn't catch a screenshot of it and it's pretty inconsequential.
Next time: the party does something reckless and unnecessary for bragging rights! Wait, that doesn't narrow it down very much. Next time: the party fights the Mega Dragon!