If Castle Rajikline could not be breached with an army, then the only way to overcome it would be with stealth. Logically this made sense, but a stealthy approach on the structure would not be easy by any stretch of the imagination. Forest bordered the moat relatively closely on two sides of the castle while the other two looked out over expansive fields. Of the two sides closest to the trees, the west wall would be the easiest to get to without detection, but easiest did not mean easy or even possible. A good hundred yards of flat land lay between the moat and the trees, and a larger number of lookouts were stationed on the west wall. Without an accomplice on the inside, the castle could not be breached by stealth during the day.
At night, under the cover of darkness, the paths to the castle seemed easier. The situation was changed, however, and it was no longer advisable to approach the castle from the forest. The ground there had been leveled and cleared of all debris, making it incredibly easy for the watchmen to spot movements in that sector. With darkness to cover movements, it was actually possible to use hay bales, ditches, and other natural cover on the other two sides of the castle to approach the walls, but anyone doing this would have to be careful. Mounted on top of the keep were four massive spotlights. Using fires and a series of focusing mirrors, the soldiers who operated these lights were able to cast powerful beams of light onto the castle grounds and the surrounding fields. The pattern of the lights' movements was pretty constant so it would theoretically be possible to use quick bursts of movement to move from cover to cover between the light beams; however, such movements were susceptible to detection by the men posted in the watch towers.
If a person were able to actually reach the moat of the castle, they would have to swim across it to reach the castle walls. This would be an easy task for someone who did not have much equipment with them, though it would not be pleasant. The waters of the moat did not flow and as such were quite stagnant and had many forms of filth and nastiness in them. Sicknesses of many sorts had been caught on several occasions from just a brief duration in the moat's waters.
Once across the moat's water, the castle wall still needed to be scaled. There were several theories on how to accomplish this with one of the most common involving the use of a grapple hook. The only problem with this was that to use such a hook required propelling it and an appropriate length of rope over thirty feet into the air to the top of the castle wall. Of course, this task would likely require a large piece of equipment like a crossbow, which brings up the question of how to swim across the moat with such a tool. For the sake of argument, perhaps a determined individual buoyed up the weapon with balloons and floated it across the moat. Using the cross bow, they launch the grapple hook over the wall and hope to heaven that nobody sees it or hears it strike the stone that it attaches to.
The next task is to actually scale the wall. This would require a significant amount of physical strength, but would not be impossible by any stretch of the imagination except for one thing. Special watch towers jut out from the wall, giving the soldiers inside a perfect view of the face of the wall. They will spot any inconsistencies or movements on the wall making scaling the thing tricky at best. Once actually on top of the wall, the person who is trying to break into the castle only has to sneak past all of the guards to gain entrance to the third floor of the keep. From there, as before, the last two levels of the keep are shrouded in mystery.