The Castle is a short day relatively speaking. Once you've made the rigorous approach, why not spend some time playing around on this spectacular peak's upper heights? The Castle's southeast summit will get your heart racing a lot more than the true summit or the east summit. To reach it, follow the Southeast Gully route to the hanging garden. Here you're surrounded by The Castle's four main summits. Your goal is the prominent summit south of the east summit described in the Southeast Gully route (when considering all four of ths summits that surround The Castle's hanging garden, the east summit is most accurately described as the northeast summit). Scramble up and over boulders to reach the notch between the northeast and the southeast summits. Check out the amazing drop-off to the east, and then look to the right to contemplate your future.
First scramble up a crack at the left (east) end of the summit. Once at the top of the crack, look right for another crack, with a convenient rock wedged in it that helps your scramble. Make the tough move up to the top of this pinnacle. You're still not on the summit, though. From the pinnacle, you have to take a several foot leap to the summit plateau, which indeed requires some courage. There are two logical jumping off points, but the smaller one on the left (south) is probably the best choice since you don't have to jump upward very much to cross the chasm. Enjoy your private perch! For the leap back, it's best to jump down to the larger, lefthand (northern) platform of the middle pinnacle.
Beyond what's already required for the Southeast Gully route, no additional gear is necessary. This scramble is only recommended when the route is completely dry. A misstep during almost any section of this short scramble would be disastrous.